that happened to me...i received an email out of no-where that BIS could not access my Gmail account. i logged onto BIS and re-entered in the password and username etc, and then it worked.
HOWEVER...after I did that...then this issue started occuring. please see the link to my other thread about the Gmail application sent mail sync issue:
Here:
http://www.blackberryforums.com/gene...-problems.html
please read that thread and tell me if you are experiencing the same problem after you got that message from BIS. make sure to follow the exact steps that i layed out in the Thread