Try adding some Modelines to your /etc/X11/XF86Config file. I have:
Code:
# Generated by the XFree86 Modeline Generator
# http://xtiming.sourceforge.net/cgi-bin/xtiming.pl
Modeline "1280x1024@60" 114.98 1280 1312 1744 1776 1024 1045 1055 1076
Modeline "1280x1024@60i" 49.50 1280 1312 1496 1528 1024 1047 1053 1077 interlace
Modeline "1280x1024@75" 156.43 1280 1312 1904 1936 1024 1043 1056 1076
Modeline "1280x1024@75i" 64.12 1280 1312 1552 1584 1024 1046 1054 1077 interlace
Modeline "1280x1024@57" 108.00 1280 1312 1720 1752 1024 1045 1055 1076
Modeline "1280x1024@114i" 108.00 1280 1312 1720 1752 1024 1045 1056 1077 interlace