Squirrelmail session premature expiration?

["Luna Kid" <listreader@neuropolis.org>]

Hi,

After upgrading some stuff, squirrelmail cannot any
more keep its session up. It more or less randomly
bombs the logged-in user off, saying:

    ERROR
    You must be logged in to access this page.

(It comes right after pressing the login button sometimes.)

Anyone seen/fixed this?

I run a fresh Debian unstable with

    apache       1.3.29.0.1-3 
    php4         4.3.3-4
    squirrelmail 1.4.2-1

Thanks a lot!
Sz.