Do you mean you couldn't use the stock UBB Code, or the additional ones (colour, size, font, etc)? If you mean the additional UBB Code, you'll need to mod all that back in again. Check the 6.6 Mods forum.
Also, are you sure you didn't overwrite the vars_*.cgi files in your variables directory (unless instructed to by the install document)? Do you get any error messages when trying to use graemlins/UBB Code?
This one's got me confused a little...
