Yeah, I get that. It hesitates for a moment when the window comes in and out of focus, but I didn't consider it a big deal because a lot of programs will do that since it can take a moment for the desktop environment (I use KDE) to redraw the borders and decorations.
I'm out of luck then. I use Gnome with Metacity and the freezing is always irreversible for me, not just momentary: the game becomes completely unresponsive, I have to kill the process manually.
No such problems with Baldur's Gate and Icewind Dale: they're using the same engine as Ps:T, aren't they?