IIS 5.0 CSR generated too long (invalid)

Problem: when you go to the site's property under IIS, you pick director security, then server certificates and do generate a CSR (certificate signing request) you may get a file that is too long and will fail to validate. what you do is create a dummy site, generate the request then process that same pending request in the dummy site. after that go to your site and choose to replace certificate. pick the cert that you just processed and you're done!take a look at this:
Thawte Support Site
and this Thawte support to generate the CSR

hope this helps!