Thickbox settings

Hi, I've just Installed thickbox in a Drupal 5.2 and when I try to go to the settings to activate it, I just get a blank page. It's like there was any bad formatted thing in the php code of that page.

Can someone figure out why it's this happenning? And if not, how can I activate Thickbox (in a configuration file, in db..)?

Thank you!