This is something we'd had to fix in our latest version, some of the fields are too big. What you'll want to do is open up the install/createtable.php file and edit it. You're looking for these 2 lines:
BBCODE_MATCH_REGEX varchar(256) default NULL,
BBCODE_MARKUP_RESULT varchar(2048) default NULL,
Change those, to this:
BBCODE_MATCH_REGEX text,
BBCODE_MARKUP_RESULT text,
After that, you'll need to wipe out all of the ubbt_ tables from the database using something like phpmyadmin. At that point you should be able to run that step again without errors.
