Spontaneous logouts on MacOS/FF4 with ZCS 6.0.12p1

[Rich Graves]

I've got at least 3 users who are getting kicked out "at random."
It's not a session timeout. They were actively using ZCS. Jetty access log shows a request for loginOp=logout.
Coincidences: upgrade from 6.0.9 to 6.0.12p1; all users running MacOS; all users running Firefox 4.0 or 4.0.1. No unusual FF extensions.
Anyone else seeing this, or have troubleshooting suggestions?

*.*.*.* -  -  [19/Apr/2011:14:19:52 +0000] "GET /zimbra?loginOp=logout HTTP/1.1" 302 0 https://mail.example.com/zimbra/" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.5; rv:2.0.1) Gecko/20100101 Firefox/4.0.1"

[rchinn]

Did you find a solution for this? I just had a user report a similar problem with Firefox 4.0.1 on a Mac. We upgraded to 7.1 from 6.0.10 a couple of weeks ago. He reports, "Since I upgraded to Firefox 4.01 and the new Zimbra - it logs out in the middle of use".

[Rich Graves]

Workaround has been to recommend Chrome or Safari. :-(
Now that I have a second site with this problem, I've entered https://bugzilla.zimbra.com/show_bug.cgi?id=59892

[steve.beeman]

Same thing is happening on my site. I tried running safari today and the same thing is occurring although less frequently. Mac OSX 10.6.7 with everything updated.
Edit: I am also receiving this often on firefox 4.0.1 as the OP submitted. Didn't think that was clear originally.