I've tried that, too. I even went into myphpadmin and deleted the tables that were created by those two products and I'm still not getting anything. Even the newly installed forum isn't working. I didn't want to risk uninstalling vbulletin if that wasn't going to do anything, so I just gave the second forum it's own database separate from the first's. No change. White screen, everywhere.

The install/install.php is the only thing that doesn't give me a white screen.