HomeCrafter is the custom wall and floor application from EA. Sometime in the latter half of the EP's being released, they conflicted and Homecrafter would no longer start. I personally do not have issues with Homecrafter, since I don't have the later EP's, but I hang out in a lot of different help forums. This seems to work for 99% of the issues.
If the following tips don't work, and replacing the executable also doesn't fix it, you may need to uninstall and completely remove the registry entries.
Tips to make HomeCrafter run:
Uninstalling HomeCrafter and removing registry entries: