PEAR Cache: strange safe mode restriction with file container

Hi I had to install my application which runs well on some servers with PHP4 in a PHP5 environment. Now there is a strange issue with PEAR Cache: Warning: mkdir() [function.mkdir]: SAFE MODE Restriction in effect. The script whose uid is 10180 is not allowed to access /home/httpd/vhosts/mysite.com/httpdocs/site/cache/inhalt owned by uid 48 in /home/httpd/vhosts/cuervoysobrinos.com/httpdocs/tools/PEAR/Cache/Container/file.php on line 339 Anyway this is the group directory that was created by the file container script at line 119. So how can it be that a directory created by this script belongs to another user? This looks very strange to me... Deleting the group directories and recreating them manually and chmoding to 777 results in no more warnings, the sub-group directories will be created but left empty. Is this a PHP5 issue? Safe_mode is also active on the other servers with PHP4, where the application runs smoothly. Or do I have to look for any kind of setting my ISP could have changed? Thanks for any comments! Markus