Master Qui-Gon is absolutely correct; the Additive Blending (In the Launcher, under Hardware Configuration) was created PRECISELY for your brand of video card, because they have a different way of dealing with transparency than most cards. It gave our compatibility programmer FITS before he came up with this solution.
From what I saw of it, the additive blending gives a REALLY COOL look to Otoh Gunga - all the bubbles GLOW instead of just being see-through. Personally, I thought it looked much more like the movie. WARNING: I have no idea what happens if you turn Additive Blending on when you don't have the ATI Rage Pro card. It may or may not look different.