It's next to impossible for apple to check the behavior of updates on every variety of hardware combinations out there. There are established workflows that are important to maintain if you depend on your system to make your livelihood.
That said, You might try deleting your fcp preferences. Try this:
http://www.digitalrebellion.com/pref_man.htm (thanks StudioX for his post earlier today)
Also, I'm wondering if there might be a compatibility problem with your video card. Check the video card in the system profiler and do some googling and searching here.
And I'm not surprised that you have lost access to a plugin. It's very common that updates cause problems with plugins.