Problems installing extensions

Hi, I'm trying to install some php extensions (some pecls, some third-party). But I have always the same problem: System: Debian 3.1 sarge, Apache 2.0.54-5, PHP 5.0.5 (also tested with 5.1.2 - the same behavior in this case). Compiling and all the extension-specific stuff works fine. But when I add the extensions to the php.ini and restart apache, the modules are not loaded an the apache error log sais: <b>Warning</b>: PHP Startup: Unable to load dynamic library '/usr/lib/php5/20041030/apc.so' - /usr/lib/php5/ext/apc.so: undefined symbol: core_globals_id in <b>Unknown</b> on line <b>0</b><br /> The extensions available in Debian's apt tree work fine (php5-mysql, php5-ldap, etc). But I tried three different extensions (APC, Mailparse, adodb) and got always the same error message (sometimes it sais "undefined symbol: executor_globals_id" but I could not reproduce when which of both error occurs). And because three different extensions throw the same error message I suppose that php is the problem...not sure about that. Greets and thanks Adrian Schneider