Dashboard Drop-Downs Not Working

I’ve been searching everywhere for an answer to this bizarre dashboard problem. None of the drop-down menus or widget openers or even the Screen Options and Help links in the upper right work anymore. I’ve tried several browsers, restarted my computer, etc.

What’s especially odd is that the other two administrators are not having this problem on their PCs. When I log in as one of them the problem persists. I do have JavaScript enabled, and I’m not having any noticeable problems on other sites.

Any help would be much appreciated.