GMail is a virus, according to Microsoft

From late last week until Sunday night, the Windows Live OneCare security software incorrectly flagged the Google e-mail service as a threat. A warning popped up when OneCare users opened the Gmail Web site, telling them that their systems were infected with a virus called "BAT/BWG.A."

According to a Microsoft representative, this was a limited false positive issue with the anti-virus protection, which is now resolved with the release of a new anti-virus signature on Sunday evening.

From: CNET