I'm using an ATI All in Wonder 128 Pro (Rage128 chipset), and an Iiyama 8515G monitor. When getting to the X setup part of the 7.0 installation, I select the monitor from the monitor list together with the Rage 128 Generic adapter (which is selected for me by default). I also select the "Customise" button as I want to select my own resolutions to use with X. When I press "Next" and get to the resolutions selection page, I can select and test 800x600 and 1152x864 resolutions at any colour depth - the tests work fine, and I can select "OK" to the dialog that appears. However, selecting 1024x768 (my preferred resolution with a 15" monitor) and "Test" causes the screen to go black (presumeably the test has failed) after which I am returned to the selection screen. Using the other "All in Wonder" or "Rage" adapter selections either do the same thing or don't work at all.
Passing to QA to reproduce.
Please ignore this defect. I turns out I am actually using an Iiyama8515F (not the 8515G I had selected from the monitor list). If I manually enter the horizontal and vertical frequency ranges from my 8515F monitor manual, all is OK. Sorry!