Hi Pete,
I haven't personally done it, but we do have customers using SCEP enrollment with Verisign. I would suggest opening a case with the TAC so that they can evaluate your logs and configuration. It's pretty tricky figuring out how to initially set up the URL/etc, but once you get beyond these pieces, unless you've found a problem, it should work fine. If you've found a problem, the TAC can assist getting a bug open for you.
Best Regards,
-pete
