Getting constant “Authentication Failed” Outlook notifications–but i’m still getting email.

Hi Folks, 

I've been successfully access 4 gmail accounts via Outlook for some time. Recently however, I keep getting those annoying bouncy pop ups with the error in the attached picture--for each of my accounts. The weird thing is nothing has been interrupted with sending or receiving emails. Everything works perfectly fine except I'm about to launch my laptop into the creek because a notice every 45 seconds about failed authentication is pushing me to the edge. I'm running Outlook for Mac 2011 version 14.4.8. I've tried re-entering my un/pw and nothing changed. Anyone? Any ideas? Please & thank you!