I found a bug just now.
If you scroll down on the list so that the top game is not visible, but its extras are, then delete the extras, you can no longer scroll back up to view the top game. At first I thought I had accidentally deleted the game from the list too, but the file size in Explorer kept growing so it was clearly still downloading (and nothing else on the list was).
- I have Theme Hospital at the top of the list, followed by the Theme Hospital extra content, then the Witcher 2 and its extra content.
- I deleted one item from the Witcher's download list (trying to move its soundtrack up to second place after the Theme Hospital installer). This caused the list to scroll down so that the Witcher's game installer was at the top of the window (but the scroll bar still allowed me to scroll up to view the Theme Hospital files).
- I then deleted a few more things, and scrolled up a little to delete the two Theme Hospital extra items, but I only scrolled up enough to view them, I couldn't see the installer right at the top of the list.
- After this, the whole of the Theme Hospital entry seemed to vanish, but as I said kept downloading.
I've not yet reproduced the issue (it is a little hard to do so without buying more games with long lists of extras after a game with a short list of extras). I did also report this through the log report system, so I hope this helps.