What driver are you using for your S3 Trio card? Are you sure it's the correct one? If I'm not mistaken, it should be the s3virge driver. When you run XConfigurator or xf86config are you selecting the proper horiz and vert rates? This will make a big difference as well. Additionally, when you're setting your default resolution rates, try to go with the largest resolution possible with the lowest color bit so you can at least narrow down the problem a bit more. If you can run X with a crappy resolution, then it's possible that your resolution is set too high. If you still can't run X, check your driver for your Vid Card. Additionally, open this file:
with your favorite text editor and see what all errors have been provided then post them here.
Hope this helps.