You may notice that when you try to login to a PSN account on your device it will tell you that your password is not correct, even tho your almost certain that it should be correct. Dont worry, this is due to a few changes that Sony made to their PSN network login.
To fix this issue, you will need to use a computer or mobile device to generate a device password.
On your computer/mobile device, goto the address
http://playstation.com/acct/device-password
login with your PSN details
Press 'Generate New Password'
This will give you a series of random letter and numbers in both upper and lower case. This is now your device password JUST for your Vita..
Your main PSN account will still be accessed using your manually created password as always, as we havent changed it. This generated code is a secondary password that you will use just for your Vita to login.
In summary : To login to your PSN with your Vita you will use the randomly generated code, to login to your PSN with other devices such as the computer or Playstation you use your manually created code as normal.