PHP Notice: Undefined property: stdClass::$cache problem

Hi,
i have just upgraded drupal 4.7 to 5.1 all went fine
after the upgrade i made two more changes
1. changed time&date of the server
2. installed a security patch for php 5.2.1 from opensuse repository with Yast
running on openSuSe 10.2 x86_64

on checking the apache2 error log i get this on every hit to the server:

[Thu May 03 23:50:06 2007] [error] [client 217.132.13.204] PHP Notice: Undefined property: stdClass::$cache in /srv/www/htdocs/includes/cache.inc on line 37
[Thu May 03 23:50:06 2007] [error] [client 217.132.13.204] PHP Notice: Undefined property: stdClass::$cache in /srv/www/htdocs/includes/session.inc on line 77
[Thu May 03 23:50:14 2007] [error] [client 88.153.136.240] PHP Notice: Undefined property: stdClass::$cache in /srv/www/htdocs/includes/cache.inc on line 37
[Thu May 03 23:50:14 2007] [error] [client 88.153.136.240] PHP Notice: Undefined property: stdClass::$cache in /srv/www/htdocs/includes/session.inc on line 77

i uninstall ed the php patch and run cron.php
still the same !

the interesting part is that i have two more sites on this server and now all sites are causing this error messages
any one have a solution on how to fix this ???