OK. "Problem" solved. My party was carrying too much weight. I guess I should have mentioned I'm completely new to this game. I realized what the problem was when I was trying whether DM Java had similar issues, and after making a huge map, tried to get past the first skeleton by giving myself dragon plates and all such heavy stuff, and of course the same "issue" suddenly appeared. (Should've just made a high level party or something.)I started playing the RTC version of DM a few hours ago, and the game was smooth at first. However, at some point already on the first level (below Hall of Champions) the game started to use 100% processor power (3.15Ghz) or thereabouts and slow down repeatedly. There was a lag between pressing a button and the related in-game action (moving, in this case). Perhaps it's not a party killer, but it felt very out of place after the smooth beginning.
Has anyone else had similar issues with this port?
Well, anyway. Now I can get back to playing the game. Sorry for the confusion!