I have a program pinned to the taskbar. After I upgraded the program (I think) the icon broke. What I get now is what you see below; that ugly default application icon thing.

If I unpin it, I get the correct icon. If I then right-click on it, the icon breaks again. If I pin it again, still the broken icon. Unpin again and back to good icon. Very annoying. How can I fix this?