I've found the reason for the segmentation faults an the core.* files.
It's a bug in the following debian lenny php package. Ist not a hardware fault. hours of testing led me to that point. The same core.* files were seen in other hardware. If tried other server environments. The fauls did'nt arrise with debian etch package.
This php ist faulty:
PHP 5.2.6-1+lenny3 with Suhosin-Patch 0.9.6.2 (cli) (built: Apr 26 2009
Segmentation fauls could not be recogniced with the package.
PHP 5.2.9-0.dotdeb.2 with Suhosin-Patch 0.9.7 (cli) (built: Apr 7 2009 20:42:41)