Processes not yielding, and lockf

["Kevin Jones" <kevwjones@xxxxxxxxx>]

I'm running an Apache server on a FreeBSD server with 494 MB of RAM and an Intel Celeron 2.4 GHz CPU.
A recent surge of traffic to my PHP site has been causing the server to come to its knees.

The first symptom is that the server won't return my page when I access it through the browser. The connection times out.

In researching, I found out that my available RAM had become cripplingly low (about 1 meg) because Apache had spawned over 100 different processes of itself.

So, I figured the way to fix this was to limit how many processes Apache would start up max, so I edited the 
httpd.conf and set MaxClients to 40 (I'm using the prefork MPM) and KeepAliveTimeout to 15.

That's fine, but now it runs out of available processes to handle requests very soon. I run "top" to see what's happening, and I see that most of the apache processes are in the "lockf" state. And a few are in "sbwait". I run "ps", and see that most of the apache processes are idle or sleeping.

What do lockf and sbwait mean? Are the processes just idling?
How do I get the Apache processes to die?

Thanks for any help.