Slow/incomplete response on subsequent dynamic page reloads

[Brian <brianko@xxxxxxxxx>]

Running Apache 2.2.8/PHP 4.3.10 on Linux 2.6.9-42 kernel.

After some tweaking, initial response time for static pages is very fast.  The first access of a dynamic page is extremely fast as well.  However, subsequent reloads are usually much slower, and many time the response is incomplete (or, the browser simply waits for a response that never comes).

I and others have tested with several different browsers from several different locations; results always the same: Dynamic pages load quickly on initial access, but reloads are slow and/or incomplete.  I'm running all defaults for directives in httpd.conf.  There is no swapping going on and the httpd process doesn't appear "hung" on subsquent reloads:  It briefly jumps to the top of the process list, then returns to idle again. Doesn't matter what PHP app I access:  The few I'm running exhibit the same behavior, even a test page displaying phpinfo().

Any ideas on how to troubleshoot, or what the problem might be?  Anyone suspect that this might not be an Apache problem, but a PHP problem instead?  Caching issue? 

  --Brian