For your reference

http://bugs.php.net/37066

if problem is not replicated without debugger, it does not mean that the problem with debugger and only.

okay, to stop ping-pong, let's move further with php.
please compile php with minimal settings.
I'd recommend to try first this:
./configure --with-apxs2=/usr/local/apache2/bin/apxs

then if it works, try the first half of the other settings, then depending on the results, the bottom half of the other settings.
If problem is in the extensions/3rd party libraries you'll find it pretty soon by dividing the list of arguments by 2 (using binary tree search, actually).
If problem happens even without the libraries/extensions, I promise I'll provide you debug version of the debugger.
Better if you contact me by email

TIA,
Dmitri.