Mebbe you lost focus on the windw you're trying to scroll in.
Otherwise, it's gotta be that teh intra-nets hayt joo.

Mouse pad, scroll pad, ftw are you talking about? If you were downloading something, I'd bet that's the problem. It's done, and you don't realize it. Click the download box, go back to your page, and you should be able to scroll again. Like I said, you lost focus of that window due to something