Access denied when uploading 40-50 files...

Hi,

Have you met anything like this:

When uploading about 40-50 files to a node - with or without Imagefield ZIP
Support - I get Access Denied page and Drupal is logging me out (!).

There is no error in Watchdog, no error in PHP error log. Huh?

I can't find any limit for Imagefield, that could be reason. Only upload limit
for a node, that is set for 50M.

Any other hints?

[running last Drupal core, all last devs from Imagefield family and CCK]

Szy.