I haven't seen a pattern to when or why this happens, and LL is the only site I have had it happen, but sometimes scrolling with the mouse wheel just stops working on this site. If I close the window and return it always works again.
I use chrome for a browser.
I realise this is very little information to go on, and it's not a mayor issue, just thought I should mention it if other people have the problem as well. Happens fairly regularly, but like I said, not with any pattern I can see. Sometimes it is in the forums, sometimes in the download section, and it's not one particular sub-forum. Seems pretty random.