Why does system preferences crash when changing screen saver?

Question

There are several posts in this same vein, here, but I can't seem to find a specific one.
I had a process that ran and accidently began removing portions of my "user" directory.  I used time machine to restore and everything seems fine now.
However, I noticed that after awhile, the screen saver would come up rather than just blanking the screen.  I decided this would be ok, so I when to System Preferences-> Desktop and Screen Saver then clicked the Screen Saver tab. I chose one of the screen savers, but didn't like it. But upon re-entering the System Preferences a second time, low and behold, there were NO screen savers listed and the process hung and wouldn't close.  I finally had to stop the process from the Activity Monitor, at which point it gave a dump. This has happened about 10 times.
When I go to /System/Library/Screen\ Savers/  there is no content there. Same goes for ~/Lirbrary/Screen\ Savers/.  So it looks as if they are gone. I have a Mac Book Pro, however, that behaves the same way (except its running Snow Leopard instead of Lion). So I don't know that's it.
I have run permissions repair and checked the disk and all is well.
I have set System Preferences to not run in 32 bit, as someone suggested, but that didn't do anything either.
I have a 2009 iMac with 4GB and about 3/4th full disk.
Could anyone suggest any more alternatives?

Answer 1

Thanks Linc.  I am not really comfortable with the re-install approach I guess, but it may be all I have left.  I tried to go back to a previous backup on Time Machine and just replace systempreferences.app but the backup wouldn't let me do that.  I have restored library in my home directory but I did so only piecemeal based on things that seemingly got disturbed.
One very odd thing... I left my computer on this morning and came back a little later and lo and behold a screen saver was running. This was a bit of a surprise, seeing that when I go to the system preferences and try to see screen savers, they aren't there and that's when the app hangs. So, apparently the screen savers are SOMEWHERE, but not able to be seen.  That's what is killing me. I feel as if its a permission problem, yet when I run a repair-permissions, it finds nothing wrong. The screen saver files are supposed to be somewhere, but I have a feeling they are hidden somehow, and because of that, I can't change anything. The result baffling part is that even in terminal mode, viewing /System/Library/Screen\ Savers/ or the home library folder, shows absolutely nothing in Finder OR terminal mode. So they are either completely gone or hiding. I have to assume the latter, seeing that a screen saver started up.
So if anyone has an idea how these files could be hiding, or where, other than the locations above, that would be a very good thing to know.