ToME: the Tales of Maj'Eyal

Not only. The character I saw it on didn't have empty hands. I went though most of the first-tier dungeons happily using a sling/shot offset and 'x' to swap. Then I got into the Maze, found some new shot, went to swap it in, and it started happening.

This happens to me too, consistently. It does seem to be related to a ranged off-weapon and switching to/from it. It's not a crash, and not exactly a freeze. The screen goes blank except for the cursor, which will move, but clicking anywhere doesn't seem to do anything. Keypresses don't seem to have...