CSR Generation in IIS 4.0

I am running NT server 4.0 SP6a, Exchange 5.5 SP3, and IIS 4.0. The sole purpose of this server is Outlook Web Access. I have successfully configured the server inside my Watchguard firewall, and have access to it across the net. I am now attemptingto obtain a certificate from Verisign. I have followed the instructions to generate the CSR, but at the very end of the procedure I receive the error “unable to generate a new key request”, with no other information. Any help would be appreciated.