ISA 2004 RPC Filter Breaks Certificates Snap-in
I really like using the Certificates MMC snap-in because it greatly simplifies issuing certificates to domain members when using an enterprise CA. Sadly enough, the ISA 2004 RPC filter kills the Certificates snap-in, and also the Certificate Request Wizard used to issue certificates to IIS and Exchange Services. Bummer.
The solution is to disable the RPC filter in the Add-ins node and then create an Access Rule that allows all IP traffic between the communicating hosts. Just make sure to remember to disable this rule and re-enable the RPC filter after you've issued the certificates!
If you don't want to go through that hassle, you can always use the Web enrollment site, or create a file for an offline request.
HTH,
Tom