Identical problem here, also on pinned tab (staying logged into GMail). Started happening a few days ago on Firefox 20, now updated to FF 26 and still happening. I go to about:permissions and delete accounts.google.com cookies and am then able to use the Gmail inbox bookmark and log back in, but what a pain this is.

You can try to toggle the browser.sessionstore.restore_pinned_tabs_on_demand pref to true on the about:config page to prevent pinned tabs from getting restored automatically and refresh only one Gmail tab via F5.

• http://kb.mozillazine.org/about:config

@cor-el I accept this as a reasonable workaround to the problem. However, it would be nice to see a solution that does not involve a workaround, or an explanation as to why a solution is infeasable.

Curiously, today, as suddenly as it appeared, my problem seems to have resolved itself. No longer do I have to delete the Google cookies on every re-start of Firefox. The open GMail tab remains open, and I am also able to access Google Drive on another tab without receiving the mismatch message. I have no explanation.

I just noticed the same thing. I no longer have a problem leaving multiple Gmail accounts open at the same time during restoration. I turned off the ""browser.sessionstore.restore_pinned_tabs_on_demand"" to check, and all works as expect. Perhaps this was a problem on Google's end?

Perhaps this was a problem on Google's end?

I suspect so. It is a problem that was reported in 2011, then everything seemed to go quiet.

I wasn't able to find any tickets or posts regarding this issue in its entirety. That is to say, I found plenty of people having this problem, but it seemed like they only ever had it once, not repetitively. Especially odd if the issue cropped up in 2011 but only started for us this recently.