reboot and then add the Gmail account back in.
Get rid of i-antivirus program, it does nothing for you.
There are currently no viruses that work on OS X
P
I have a g-mail account and Mail is set up to link to it. As of yesterday it refuses to work. I have tried re-starting Mail, re-starting the whole computer and even re-installing the whole iMac applications CD but nothing works.
My g-mail account is still fine when accessed through my iPad or via Safari on the Imac itself so its clearly just the Mail application.
I even downloaded the i-antivirus program in case there was a virus problem but it says my system is clean.
The machine is a nearly new iMac (Nov 2010) and has otherwise had no problems.
Has anyone seen this problem before and have any idea what I can try?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic