System preferences freezes

Info:
Had my MBP 13" for almost 2 weeks now.
Running Mountain Lion.

Problem:
Last night (13-14 hrs. ago) I changed my desktop wallpaper from the default one to some wallpaper I found on the internet. Changing was a breeze. Nothing came up.

But, just this afternoon, I decided to take a look at the other wallpapers in system preferences>desktop and screensaver but it kept on freezing/not responding (had to force-quit every time).

I googled the problem and found things such as: deleting com.apple.desktop.plist (from Library>Preferences) and com.apple.systempreference.plist (from Library>Cache) both from the library which I did and worked like a charm at first

When I rebooted my MBP (it was included in the steps after deleting the files), I found out the wallpaper I took off the internet is gone and once again replaced by the default (which I don't like that's why I changed it in the first place). I opened the system p>desktop and screen saver once again and poof it's not freezing anymore BUT when I selected an iPhoto folder from the selection, it started freezing again!!

This problem is really driving me nuts. I just want to change my goddamn wallpaper. Why does this have to happen??


CURRENT SITUATION:
Desktop wallpaper back to default and "system preferences>desktop and screen saver" freezing once again (the original problem). Meaning to say, I've already deleted the files above (but I think they get replaced right back anyway) but I'm, again, stuck with my original problem.

UPDATE:

I did it again. I deleted the two files again so the desktop pictures would load properly. But the iPhoto folder still makes the window freeze.

As you can see form the attached snippet, the desktop pictures loaded properly this time but as I clicked the "May 5, 2011" (iPhoto album/folder) it froze once again (with the rainbow wheel but not visible from screenshot)

BUT AGAIIIN, after force-quitting the non-responding window, I tried opening the desktop&screen saver and yeah, ORIGINAL PROBLEM, i.e., second attached picture (nothing would load, instant freeze!)

Bump