Mail keeps asking for my gmail password

I haven't used my MBP in several days. I opened Mail today and it keeps asking me for my gmail password. I have it set up to access my gmail using IMAP. It had been working fine as of 4 days ago. I went to my gmail account and signed in using the same password and it worked fine. I tried changing my password. It still didn't work with mail but worked fine using the web access. I deleted my gmail account and then added it back using the settings specified by Google. Still doesn't work.

I'm using Lion and Mail version 5.2. Anyone have any suggestions on how to fix this?

Well, it's working this morning. Guess it was something on Google's end.

I've had that problem several times. Usually, if it clears up without you doing anything different it is on their end.