A VGA cable carries an analog signal,
and the maximum length decreases as the resolution goes up.
1024x768 can run effectively over a 9 meter (30 ft) cable, but
1600x1200@60Hz won't work well past 1 meter (3.5 ft).
Your options are to user repeaters to increase the distance
to over 600 ft - http://www.networktechinc.com/cat5-vga.h…
or use DVI instead. Since it's digital it can carry longer, even with high resolutions, up to 30 ft
Hope that helps...