Facebook and Twitter integration not working

I'm have trouble using Facebook and Twitter integration in Mountain Lion. When I click 'Click to Tweet', or 'Click to Post', nothing happens; I don't get the notecard looking thig, and it's like I never clicked the button. Same thing with sharing from an app, except for Twitter. I receive notifications from both just fine, but I'm unable to post. I can tweet something from the sharing menu (link to a webpage with Safari, for example), but I cannot send a tweet using the 'Click to Tweet' button in Notification Center. Also, I cannot post to Facebook by neither sharing nor the 'Click to Post' button. So far I have tried sharing with Safari, Finder, and Preview, all with the same results. (Facebook sharing with iPhoto does work, but I don't believe that is integrated with OS X.)

I have also tried the following, with no luck:

• Checked my settings on the Facebook and Twitter sites.
• Removed my acounts and re-added them.
• Obviously, my internet connection is working.
• Added my Facebook account to the 'Guest User' account, and another administrator account.
• Had a friend add his Facebook account to his own (limited) account on my computer--he could not post to Facebook either.

I believe the last two things I tried indicate that this is a system-wide problem. A couple more things to note: 1) there is no kind of error message; it just sits there, like nothing happend, no 'spinning wheel' or anything. 2) It DID work before. Twitter worked when I first upgraded to Mountain Lion, and Facebook worked when I installed the 10.8.2 update. I don't use either often enough to know when exactly they stopped.

Here is a video illistrating my problem.

It's been driving myself crazy with this over the past few days, and can't seem to find an answer anywhere. I also seem to be the only one with this problem.