RPC over HTTP Proxy

To All:
I setup RPC over HTTP a while back and everything was
great. Then one day, my Default Application Pool in IIS
starting failing. The cause was listed as ISAPI Filter
Failure and pointed to RPCProxy.dll. When this ocurrs, all
my web sites are down as the Default Application Pool is
down. I have removed the RPCProxy Service and everything
is fine... if I reinstall the server, I get the same error.
There is nothing I can find anywhere on Microsoft's
Site about this error and I don't know what has changed
that would effect the service, but I am getting really
tired of this... Any ideas anyone?
Gary