Whats causing Drupal to freeze when creating/editing a mini-panel? I'm quite new to drupal.

Drupal has been freezing for me when I try and create or sometimes edit a minipanel. Once I select the panel layout and start adding content it just remains in the lightbox 'grayed' state and wont let me click or do anything. It's almost like it's trying to load but I've left it for an hour and it's completely frozen. 

I've tried on Firefox and IE10 and get same issue. Also upgraded my drupal from 7.23 to 7.24 today so a completely new core is running but still hangs like this. 

I haven't fully explored everything yet in drupal so I don't know if other sections will do this. So far it's just the minipanels section. 

Does anyone have any suggestions? Thanks.
By the description of your problem, it seems to being caused by a Javascript error.

Try to check with Chrome DevTools, Firebug or the debug tool of your preference on the browser, go to "Console" tab and look for Javascripts errors or maybe on the "Network" panel to check for XHR (ajax) problems.