Icons appear as blocks (windows 8)

Some windows 8 icons just got corrupted (i have no idea how) and now appear as blocks. Many icons work fine... many don't

Any idea how to fix this?

Answer

It's very likely that the cause of the problem is Segoe UI Symbol font that got corrupted for some reason.

Just get the font from somewhere (from here, for example), re-install it, and perhaps restart Windows.