PHP Fatal error: Out of memory (Apache crash)

[solinem]

Hi:
I am trying to find a solution for an error that consequentially leads to Apache Server crash.
Following is the message as seen in the error.log file:
PHP Fatal error: Out of memory (allocated 786432) (tried to allocate 32768 bytes)

SERVER CHARACTERISTICS:
* Windows 2008 Enterprise Server
* PHP 5.2.6
* Apache/2.2.4 (Win32) DAV/2 mod_ssl/2.2.4 OpenSSL/0.9.8e
* RAM=8gb,

PHP SERVER PARAMETERS:
* max_execution_time = 720
* max_input_time = 360
* memory_limit = 5120 MB

After a few messages like this, the server ends with the message:
[notice] Parent: child process exited with status 255 -- Restarting.

Whenever it happens, I don't see a substantial rise in memory usage (well under the 5GB established in the configuration)
I think part of the problem is originated because the server is not releasing memory, and data is building-up.
It is surely a misconfiguration of my server
I have searched everywhere but didn't found a satisfying solution.

[jarofclay]

We are also having the crashing issue with Apache on Windows Server Standard 2008.