Why can't I disable a module? I installed Drupal Chat just to try it out. I couldn't get it to work and now I can't disable the module.

In /admin/modules, the check box is selected but not enabled. i.e. it is active and I can't deactivate it.

Can anyone help me?

(and, once disabled, how can I un-instal it?)  



Update: I forgot to mention that there are no dependencies on the module.
usually if conventional uninstall wouldn't work i'd try clearing the module's entry from system table removing tables from the module installation (after backing up the data) clear the cache and reinstall.. hope it works for you ...cheers!!