When I try to use GMail Offline in Chrome it goes into an infinite loop, requests alternating between https://mail.google.com/mail/mu/mp/411/?mui=ca and https://mail.google.com/mail/mu/mp/511/?mui=ca.
I found several articles dating back to 2009 that say this problem can occur when switching back and forth between Google accounts, which I was doing when the problem started. However, trying the proposed solutions of clearing or disabling the cache and/or cookies had no effect.
I can still use the regular GMail. I have also tried logging into and out of the online GMail accounts and that didn't help either.