Have you tried contacting Runic directly? The TL1 site has a few pointers to solve problems already at http://www.torchlightgame.com/support/
and suggests to contact firstname.lastname@example.org
in case the problems persist.
Do take into consideration that we're nearing the TL2 releasing date, which is going to cut into Runic's time on the boards. While I understand the frustration, your problem seems to be quite unique: most likely the ones who've read the post couldn't help.
Make sure you have an up to date OS and that you are using the last version of the graphical drivers for your machine. Try the tips from the TL1 site. If it still won't run, contact Runic at the mail given before. Opening a ticket (or in this case mailing the support team) is usually a much better way to ask for official help.