"new cache feature": Apache 2.2.3 comes with built-in caching (mod_cache.so). Starting with Apache 2.2.3 the caching feature is suppose to be production grade.

I count as a crash when Windows generates a file in the folder C:\WINDOWS\PCHEALTH\ERRORREP\UserDumps
it will also produce the line (Parent: child process exited with status 3221225477 -- Restarting.) in the Apache error.log

This is a feature you might have turned off on your Windows 2003 Server.
Most of these crash are transparent (they do not impact the site). You just noticed a 15s delay while it is creating the ~20MB dump file. You are probably experiencing these "crash" without noticing it.

Although you get some decent traffic your PHP application might not be as heavy as a "Drupal + Gallery" 2 site. That probably explains why you get only 5 (Parent: child process exited with status 3221225477 -- Restarting.). If you are sure your site has no further problems no worry to have.

However the fact that you have un-explained lines in your error.log could be a cause of concern. In the future you might experience more erratic behavior. Maybe today, some of your user do, without you knowing ?

Some configurations are more stable then others. Since I started tracking the "dumps" I pretty much got all my Apache stable, now since days (no dumps or none of these "Parent: child process exited with status 3221225477 -- Restarting" ...).

Once I feel all my stuff is very stable, I will start exploring new combinations.

If you don't mind sharing:
Do you think you application is PHP "heavy" (like Drupal or Gallery 2) ?

Did you set any httpd.conf directive to a none default value ?

Did you set any php.ini directives to a none default value ?
Specifically what do you have for:
output_buffering =
allow_call_time_pass_reference =
memory_limit =
variables_order =
register_globals =
register_long_arrays =
register_argc_argv =
auto_globals_jit =

Thanks,
Chris

PS: These "crash" could be related to image rendering. I'm not positive about that at all, just a guess.