The bugs manifest themselves in a number of ways, 'like' buttons disappearing, search not working, insights not working, etc, but here's the main one:
A lot of people are having problems with switching between identities in their facebook account.
The Problem: When they click Account and choose 'Use Facebook as Page' the dialog box comes up and they can choose to be logged in as any of their pages. So far, so good. But, when they try to switch back, facebook crashes.
You could only get back to your main account by logging off and logging back in, but...
The Solution: Bizarre as it may seem, the solution (until they fix the bug) is to change your language setting to English (US).
Don't click the language link at the bottom of the page, it probably won't work, go to Account Settings and alter it under the Language tab. No save button, it should just work now.
(Sorry, not got a solution to non English speakers)
By the way, this workaround seems to solve some of the other issues too.