Can you post a backtrace which shows where the error happens?

http://bugs.php.net/bugs-generating-backtrace.php

Now I know, that session.auto_start need to be enabled. Thank you.

session.auto_start        = 1
session.save_path         = /tmp
session.gc_probability    = 100

Program terminated with signal 11, Segmentation fault.
Cannot access memory at address 0x200d4080.
#0  0xb79b in php_readdir_r (dirp=0xfdac0, entry=0xefbfd39c, result=0xefbfcf34)
    at reentrancy.c:130
130                     memcpy(entry, ptr, sizeof(*ptr));
(gdb) bt
#0  0xb79b in php_readdir_r (dirp=0xfdac0, entry=0xefbfd39c, result=0xefbfcf34)
    at reentrancy.c:130
#1  0x1d464 in ps_files_cleanup_dir (dirname=0xe136c "/tmp", maxlifetime=1440)
    at mod_files.c:168
#2  0x1d725 in ps_gc_files (mod_data=0xd8630, maxlifetime=1440,
    nrdels=0xefbfd8e4) at mod_files.c:292
#3  0x1be9b in php_session_start () at session.c:933
#4  0x1d0fa in php_rinit_session (type=1, module_number=3) at session.c:1396
#5  0x68a48 in module_registry_request_startup (module=0x110a80)
    at zend_API.c:838
#6  0x6a0a1 in zend_hash_apply (ht=0xdb4d4,
    apply_func=0x68a30 <module_registry_request_startup>) at zend_hash.c:692
#7  0x66c56 in zend_activate_modules () at zend.c:490
#8  0x4523 in php_execute_script (primary_file=0xefbfd9ec) at main.c:1135
#9  0x26d5 in main (argc=1, argv=0xefbfda28) at cgi_main.c:706

This is fixed. Please try: http://www.php.net/distributions/php-4.0.4RC3.tar.gz

--Jani