What are the other session related php.ini values you have?

--Jani

Incorect interpretation session.gc_maxlifetime parameter, the other session parameters:
session.save_handler      = files
session.save_path         = C:\PHP\sessiondata
session.use_cookies       = 0
session.name              = PHPSESSID
session.auto_start        = 1
session.cookie_lifetime   = 10000000
session.cookie_path       = /
session.cookie_domain     = 
session.serialize_handler = php
session.gc_probability    = 100
session.gc_maxlifetime    = 360000
session.referer_check     = 
session.entropy_length    = 0
session.entropy_file      = 
session.cache_limiter     = nocache
session.cache_expire      = 1
session.use_trans_sid     = 1

You do understand that with this setting:
session.gc_probability    = 100
the garbage collection is started every time
you run a script? (ie. 100 = 100%) 

How did you found out that the session is removed?
Any example scripts? It sounds really odd that 
36000 didn't work but 360000 did.

--Jani

The session.gc_probability set to 100% during experiments with lifetime. I expected some king of timeout of my site during subsiquent acceses. So I started to experiment with that and I wrote what I got. The script examples is any with session_register, with session.auto_start enabled, but I tried with session_start and got the same result. I gues that this might be something with time interpreting on the Win32 platform, cause the problem seems to be solved when life time set to more than 24 hours.

It could be file locking problem.
Please test with 4.1.0 and snapshot, and report the result.

http://snaps.php.net/

No feedback. Closing.