Every once in awhile, after enabling or disabling a module you will suddenly find yourself locked out of your website - only able to see a blank white screen. Some people call this the Drupal White Screen of Death, I call it a huge hassle.
Now that I'm working in Drupal 7 with a lot of modules that are still in alpha/beta/dev this issue has happened a few times lately, so before you go running off to reinstall or restore your db from a backup, here is my quick fix that should get you back online:
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);
This will make Drupal display errors for you, so you can get an idea of where the problem is.
The last time I got the white screen of death, this was the error message:
Fatal error: Class 'Profile2TypeUIController' not found in \sites\all\modules\entity\entity.module on line 937
Basically, when I disabled the Profile2 module and cleared the caches - it didn't really clear all the caches and the entity module was having a wobbly because some function from Profile2 can no longer be found.
* I always save a backup of my database before I do this, just in case I accidentally select an extra table or something unforeseen happens.