Hey mate, nice looking app you got there :). I have downloaded it aswell as the source.
Also the source is nice and clean. I where bothered that the column sort wasn't working, so i looked into it. The problem was the headers (installed, ....). If you turn those off, the sorting works alright.
So i implemented a little hack for it:
At private void _addonListView_ColumnClick(object sender, ColumnClickEventArgs e)
Replace at the bottom the sort with:
I know its dirty, but it works and its fast so. I will look what i can do to improve it further.