I just tried to do a completely vanilla install of 7.3.1. The install script dies out during the creation of the tables, but I can see in MySQLAdmin that the tables are created. I browse to the forum and see the install that failed, but is partially there.
This is the debugging output...
Generated in 70.079 seconds in which 0.020 seconds were spent on a total of 11 queries. Zlib compression disabled.
So a generic install of UBB is having the SAME result! Dreamhost says that the problem is our scripts...but this is a vanilla install...no customization at all. I had asked Dreamhost to look at it again, but I'm at a loss here. Its like something changed with PHP or something and it is only impacting UBB (an not our other PHP based software, including Photopost).