I experienced a bug in LR scrolling behaviour within the library module. To describe the problem best, I recorded a screencast video with audio comment that I uploaded to my webserver:
In short: Scrolling with the mousewheel over folders in LR's library module doesn't work properly.
Here is what I know:
1) The bug doesn't always occur. Sometimes scrolling works for a couple of days, but most times it doesn't, which is annoying, of course.
2) I could only reproduce this bug as shown in my demo video in the library module when trying to scroll with my mousewheel over the folders or publishing services. Everywhere else, it works fine.
3)The bug seems hardware independent: I experienced it on my laptop as well as my desktop (one Win 7 32bit, one Win 7 64bit; two different mice, one by MS one by Cherry).
4) I experienced this bug for quite a while with different versions of LR (currently 3.5, but the earliest version I used was 3.2)
I hope this helps to figure out the problem.