i've been playing duke3d on my 98se p3 system with an asus gf2 gts and noticed several issues. running the game at 800x600 (from windows), i get some weird "rogue" frames once in a while that show up for a split second; this isn't extremely common, but it happens about every few minutes on average, so it's definitely noticeable sooner or later.
what i then found by pure chance is that when i load the 4th episode and press esc and just wait, the game will lock up after a few minutes. not sure if this is specifically related to the menu screen but i've been able to reproduce this 3 times so it's not a fluke, and i verified that nothing is overclocked. not sure if it matters but driver is one of the late forcewares, either 61.76 or 71.84.
for testing i plugged in an old s3 vision868 2mb card and simply ran the game without installing any driver in windows or loading any TSR, couldn't reproduce any of the described issues. of course the game was locked in the 20s but i suppose that's fixable with a driver/TSR. what's interesting is that it automatically put out a 84 hz (or something like that) signal whereas the nvidia was stuck at 60hz...
edit: just noticed that "flashing" actually is noted for gf4 and up, however only with 1280x1024 which i am not running.
edit2: s3vbe20 makes it run in the 26-60 range, with the fps strongly depending on scene, not sure if that is how fast it is supposed to run?