I don't know why, but - on an old machine too - I had to correct HorizSync and VertRefresh manually. The XFree documentation says that a resolution does not work if it would exceed VertRefresh. I asked the vendor homepage and the owner of the monitor and altered the numbers : Section "Monitor" Identifier "My Monitor" VendorName "Unknown" ModelName "Unknown" HorizSync 31.47-79.98 VertRefresh 50-75 now works. Georg