If you are using Google Mobile in “Microsoft Exchange” mode for your iphone, you will occasionally run into an odd error informing you that your password is not correct, it will say:
Password Incorrect
Enter the password for the exchange Account “Account Name”
Don’t worry, your password is still correct. For some reason you have caught the ire of google’s security captcha. To cure your ills, go to a computer and point your web browser to https://www.google.com/accounts/UnlockCaptcha (or if you are feeling lazy http://goo.gl/phGwL)
You should find that all your problems go away and the nag screen will go away.