I dont know if this will help anyone, but occasionally the problem is on google's end. They dont like you updating your email with pop in shorter spans than 15 min. If they see that you're updating your email too often, they will block you from pop access. (or at least this is what I believe happens) They do let you reset this somewhere. Sadly though, I have lost the link to that. If I find out where to do that, i will post the link.
-EDIT-
Here it is:
https://www.google.com/accounts/DisplayUnlockCaptcha
I guess they will let you back in after 24 hours but this will reset a lockout instantly.