Dialog Window Issues
Like other programs, SketchUp uses the operating system's default browser to work with window dialogues and access the internet, if needed. The dialog window is actually known as a webdialog. The controls for a webdialog, like buttons, menus, etc, come from the default browser that comes with the operating system. The other burden of relying on the OS provided browser, specifically Internet Explorer, is that they handle all network security and proxies through that browser rather than a setting at the operating system level.
At times some browser maintenance many be needed to optimize performance and fix cookie issues even if you do not use Internet Explorer or Safari to surf the web. It also can affect Dynamic Components, Add Location, 3D Warehouse access, Generate Report, and other features, including plugins that open a dialog window in SketchUp.
SketchUp Knowledge Base Troubleshooting Connectivity Issues within SketchUp.
NOTE: Anyone who uses SketchUp 2014 should update the Dynamic Components extension through the Extension Warehouse. The initial version of "Dynamic Components" extension had a bug that broke "Generate Report". Luckily, there's a fixed version available now.
To update your "Dynamic Components" extension, you'll need to run SketchUp, open the Window -> Extension Warehouse. Logon to the site and then search for "Dynamic Components" and click the Install button.
NOTE: People still using SketchUp 6 - 8 are using a product once own by Google. All SketchUp features requiring an internet connection are being redirected from Google server URLs to servers now owned and run by Trimble Navigation, SketchUp's new owner. On June 1, 2015, the three-year contractual obligation to perform those redirects ended. That mostly affect SketchUp 8 and SketchUp 2013.
In January 2014, Google dropped support of Chromeframe for Internet Explorer - a browser helper object that added modern browser features to dated versions to Internet Explorer. This will mainly affect people using XP - which only supports up to Internet Explorer 8 - and Microsoft stopped support for XP on April 8, 2014. So internet-connectivity issues may continue for XP-users despite the troubleshooting tips listed below.
Update to the latest browser
The first thing to do is clear cache and cookies.
In SketchUp, log out of your SketchUp account through the Help menu.
Close SketchUp.
Clear browser cache and cookies | Microsoft support
Internet Explorer
Open Internet Explorer
Go to Tools > Internet options > General > Browsing history > Delete > Temporary Internet files and Cookies > Delete > OK.
Safari
Open Safari and go to File > Reset Safari... which will clear you cache, cookies, history and anything else it sees. If you've added any plugins to the browser then you may need to reinstall them.
In Internet Explorer, go to Tools > Compatibility view settings and add SketchUp to the list by adding the URL to the 3D Warehouse, or another SketchUp-owned site. The sketchup.com site will be added.
More tweaks if clearing the cache and cookies in Internet Explorer4 are not enough.
In Internet Explorer, go into Tools > Internet Options > Security > Trusted Sites > Sites and make sure that http://sketchup.google.com, http://www.google.com/accounts (and anything from trimble.com) are whitelisted.
While in IE Tools, check that Internet Explorer is set to "Moderate" security settings and disable Protected Mode, both of which will restrict Javascript usage which SketchUp needs.
Java may need to be updated.
Check if you got a Windows update where Internet Explorer was somehow automatically set to proxy mode. Try to reset your Internet Explorer settings to default - maybe (maybe) that will help.
Update to the latest version of Internet Explorer that your operating system will support. The latest version supported in XP is Internet Explorer 8.
Internet Explorer browser test. Open an Internet Explorer window:
Try opening 3dwarehouse.sketchup.com. It's a normal, port 80 kinda web site, so one would think it would. On XP, SketchUp only support IE8, so confirm that you have IE 8 (Tools->About Internet Explorer will display the version).
Try opening this url in Internet Explorer: http://www.google.com/ncr (ncr stands for "no country redirect"). If you can get to that and you're at least in IE8, things should work. SketchUp checks to see if you have an internet connection before doing more expensive actions that would just leave you hanging. You DON'T have to have Internet Explorer up and running while running SketchUp, but by hitting that page, it probably caches something that makes it speedier for SketchUp.
Not all countries (like China) and corporate environments will care to allow SketchUp to ping a google address to test for connectivity. In those cases, the test URL can be changed by editing SketchUp's DAT file. See the Knowledge Base for instructions.
Sometimes it helps to reset your Google Account status through SketchUp on Windows machines as well:
Click the logon button in the lower-left status (the G icon in SketchUp 2013 and earlier) and sign in to your Google Account.
Open SketchUp.
Click the logon in the lower-left status bar (the G icon in SketchUp 2013 and earlier.)
If you're signed into your Google account, Sign Out of your account.
Close SketchUp.
Open Internet Explorer (it has to be Internet Explorer even if your default browser is something else, like Firefox or Chrome).
Go to www.google.com.
If your email address appears in the upper right-hand corner, click on it and select Sign Out.
With Internet Explorer still open, navigate to http://support.google.com/sketchup/.
Click the Sign In link in the upper right-hand corner and log into your Google Account.
After signing in, close Internet Explorer and open SketchUp.
Check internet connection speed
SketchUp's connection to the internet can time-out if the speed is slow. If SketchUp sees a slow, inconsistent speed, it might be slow enough for us to think that you're on such a slow network that it wouldn't want to have you download a lot of data to geo-locate a model. For example, a speed of 824ms (milliseconds) is bad while 29ms is quite good.
Start > Run > type cmd (that opens Command Prompt) > press OK > type ping google.com > press Enter on the keyboard.
(Another way to access your command prompt is go to Start > All Progams > Accessories > Command Prompt.)
Mac
Open terminal and type ping -c3 google.com
If you are getting higher ping speeds, try multiple times. If your network bounces like that, eventually it'll work.
Reset Browser to default settings
There has been a report that a Windows update reset someone's Internet Explorer setting to a proxy mode - which disrupted program functions that relied on the program using the integrated operating system browser. Also malicious software can change your internet browser settings.
Reset Internet Explorer Settings from Internet Explorer's Tools > Internet Options > Advanced tab.
If the 3D Warehouse appears to be loading OK despite the error messages, you can probably ignore the messages (which is Microsoft's recommendation). You can disable script debugging by going through Method 1 of this page:
http://support.microsoft.com/kb/308260
There are other methods to troubleshoot script errors on the same page which you may consider exploring as well.
If the 3D Warehouse and/or Extension Warehouse are not loading correctly, try the other tips listed in this section - like update Java, update Internet Explorer to the latest version your operating system will allow, clear temporary cache files, etc. Also see How to troubleshoot script errors in Internet Explorer.
Use a personal Google account email to sign-in. Google Apps accounts do not work. Business accounts have to respect a myriad of international laws which gets messy...
If there still is a problem downloading components from inside SketchUp, navigate to the 3D Warehouse or Extension Warehouse from an internet browser of your choice.
Suggestion: Regular use of the free program CCleaner is a good way to keep unnecessary crap from cluttering up your system - and its default browser.