[JKT]

It is most likely to be a problem with either the History and/or the Cache - delete the three different history files in the folder and try again after moving the rest back. You might also want to delete the cache for OmniWeb (inside ~/Library/Caches iirc). If that doesn't help, discoonect from the Internet and launch OmniWeb, then close any tabs that might be the source of the loading problem.

In the future, if this happens again, hold the shift key as you start up and the will launch OmniWeb in a blank, new Workspace. It'll help you to diagnose if the problem is due to one or more of the tabs you previously had open.