How to fix Gmail incorrect password/user name error on iPhone?
Sometimes the iPhone mail app will intermittently stop getting Gmail and the dialog box below will appear. The message "The user name or password for imap.gmail.com is incorrect" can show up even if you have made no changes to your Gmail account settings on the iPhone.
Here are instructions on how to fix this problem should it occur on your device:
1. Quit all mail clients that are accessing the affected Gmail account. This means the Mail app on the iPhone and any other place you are accessing your Gmail from such as a computer.
2. Open Safari on the affected iPhone and navigate to this page: http://www.google.com/accounts/DisplayUnlockCaptcha
3. Enter your full Gmail address, password and type the characters you see in the picture. Touch the unlock button to verify your account.
4. Open the Mail app and your Gmail access should be restored.