Same topic but seems it gives an answered you already tried gcdrom.sys. Maybe there is something you missed...check out the topic above and then goto the site. It should work....but I have never needed to use it so idk.
This is the link for other people who are having issues aswell:
Visit the UBCD Wiki: http://wiki.ultimatebootcd.com
Please check your UBCD
ISO MD5 Hash Sum
; May prevent issues later on by not having an exact copy.
Currently Working on Common Issues and Repair Tips
on the Wiki.