Hi,
Thanks for your answer.
You didn't mention reviewing the system log files for PHP and httpd. Also look at admin/reports/dblog to see if there is a relevant message.
I don't have direct access to the server, but I'll try to get the logs and check them. On my test machine, I checked the logs. The only thing I found was these 404 errors:
[Mon Oct 08 10:09:47 2012] [error] [client 127.0.0.1] File does not exist: C:/Program Files (x86)/Apache Software Foundation/Apache2.2/htdocs/themes, referer: http://localhost/flavonmax/admin/build/menu/item/1964/delete
But this is because Drupal isn't in the root dir on my test server (on the production server, it is in the root). Besides, production server runs Windows Server 2008 with IIS, while the test server is Windows7 with Apache 2.2
Also tried /admin/reports, but I don't have dblog there, the only thing I can choose is status report.
I don't know where the PHP log files are.
Have you tried different browsers to see if the effect is the same? I'm guessing you've overrun some environment related maximum of some sort and the differing browsers makes no difference but finding which one is going to be a pain. Maybe the overrun is the file size or column size depending on how you store sessions (file based versus db based).
Yes, I tried on Firefox, Chrome, Opera and IE. My home PC runs Linux, I'll try on it, but I doubt that this is the problem.
Meawhile I updated PHP in hope this helps, but the issue is still there.
Can I safely empty the sessions table? I think that maybe that'll help...
Thanks, Balazs