ToME: the Tales of Maj'Eyal

This has been happening for quite a few versions (before 1.0.0 at least), and I've never quite fathomed why... When I load up the game, the characters running around in the dungeon, well, don't, it's just a static screen. This is only the case when it first loads, though. If I toggle the disable background button twice, everything starts zooming around, and I come back to the title screen after playing, it's fine also. Much earlier versions of ToME never had this problem.

Is there something I need to adjust here?