Apache dieing and processes not cleaning up

Hi,

I'm using Apache 2 with Red Hat 9 (Kernel 2.4.20-8).

Basically after a couple of days of running Apache just grinds to a
halt, and needs a restart to get going again. I have looked in top etc
and there is about 30 different httpd processes running and all
together are using up pretty much 100% cpu and some of the processes
have been running for days, shouldn't they clean themselves up?

My httpd.conf file has the following set:

StartServers 8
MinSpareServers 5
MaxSpareServers 20
MaxClients 150
MaxRequestsPerChild 1000

My server is Intel 2gig with 512Mb ram. I would include a printout
from the top screen but I have just had to restart apache so all the
processes have gone for the moment but basically about 30/40 appear
eventually, some days old, and altogether use all the CPU.

Does anyone have any ideas?

Thanks,
Chris