It's very hard to scroll the list of trainers by scrolling the mouse wheel. It normally works in the webpage part but to work in trainer list area instead, you're forced to click on a very small area between trainer tiles and the scroll bar(about 5 pixels at most in width, as long as the scroll bar in length) Otherwise the only other way of scrolling is dragging the scroll bar around. Clicking anywhere on the tile of the trainer(as long as it isn't on a button) takes you to the download page, (or at least tries to do so) therefore greatly limits the area to make it mouse scrollable.
Everything else works perfectly though.
I too experience this issue and I'm using a regular Microsoft wireless mouse. Maybe you can send us your system specs and I can compare to mine and try to find a common denominator.