RPC Server not Available Error

I have put Certificate Authority Services directly on my Exchange 2003
server. Now that I want to install a certificate from my system I am
getting an RPC Server is Unavailable error. I can go into IIS and start the
process of requesting the cert. All of that finishes completely and now I
have my certreq.txt file.
I'll go into IE and start the process there but once I paste the content
of my certreq.txt file in the box and hit Next that's when I get the error.
I have already tried changing the RPC Service to use a local admin account
(I had this problem before on an XP system and could not get Message
Tracking in Exchange System Manager to run and was told to do this to fix
the problem) but I still cannot get it to work properly.

Any help would be greatly appreciated and thanks -
Jon