When I purge cache, Bridge just freezes. I've let it 'purge' for up to 6 hours before force quitting.
That's not normal behavior, first try restart Bridge holding down option key and choose both reset prefs and purge central cache.
This means you will have to reset custom pref settings (not a big task unless you have tons of custom file type associations set) and you have to recache your files (takes a bit of time depending on amount and file size)
If this does not work you need to provide more details about what version of Bridge you are using and what version of OSX. How many RAM you have installed and how many free disk space is left on your system.
I have got the same dialog box in a german version. But my Bridge does still work then .. no freezing. But this dialog comes everytime when I start the bridge. I have already cleared all cache ... but no improvment.
Using MAC 10.8.4
I have already cleared all cache ... but no improvment.
Then use the hard way, find your user library (by default hidden per 10.7, use finder menu Go with option to show the user library).
Go to the user library:
User (your username) / library / caches / Adobe/ Bridge CC. In here are a plug in and and folder called cache.
Move both items to the trash and restart Bridge again. The deleted files will be replaced by new and empty files. You need to recache the lot again but this takes only a bit of time.