Thanks for the advice. Unfortunately, the (Award v 1.16) BIOS I'm running does not permit me to set the window for AGP. In fact, the only choice I have is AGP on or off. The refresh rate was, in fact, 85 Hz. I ramped it down as low as 75 Hz only at 1600 x 1200. It would lock even at 640 x 480 which, IIRC, was running at 120 Hz.
What's that about the Radeon not being well supported by XF86 4.2? I was under the impression that the Radeon 8500 and up were fully supported and that the 7500 is fully supported with the DRI driver?