SPN settings for CA web enrollment ? (errors while requesting for a certificate)

Hi,

I have configured CA web enrollment according to the guide at

http://blogs.technet.com/b/askds/archive/2009/04/22/how-to-configure-the-windows-server-2008-ca-web-enrollment-proxy.aspx

My configuration as follows,

• -      Configured the CA web enrollment on a server other than the CA serve. Server name is FABPKICRL01
• -      Constrained delegation with custom account for AppPool identity. Custom account name is fab.com\iiskerbsvc
• -      The URL for accessing the web enrollment is https://pki.test.fab.com/certsrv
• -      SPN settings, setspn –s http/fabpkicrl02 fab\iiskerbsvc and setspn –s http/pki.test.fab.com fab\iiskerbsvc
• -      The identity of the iis server DefaultAppPool is fab.com\iiskerbsvc

But when I launch the ca webenrollment page and go to request a certificate, I get the following error,

Request Mode: 

newreq - New Request  



Dis

(never set) 




Disposition message: 

(none) 




Result: 

The RPC server is unavailable. 0x800706ba
(WIN32: 1722)



COM Error Info: 

CCertRequest:: The RPC server is
unavailable. 0x800706ba (WIN32: 1722)



LastStatus: 

The operation completed successfully. 0x0 (WIN32:
0)  



Suggested Cause: 

This error can occur if the Certification
Authority Service has not been started.

I double checked whether the CA side and it is running. I can also request certificates from the web enrollment server using mmc.

Can this be a problem with the SPN settings ? or what could be the issue for this error? 

Thank you