Are there any situations where a DVI-D dual-link cable can't be used in place of a single-link cable?

Question

As far as I understand, DVI-D dual-link cables (24 pins) should be backwards compatible with single-link cables (18 pins).

However, my monitor is working fine with a short single-link cable, but giving me the following error message when I try to use a longer (5m) dual-link cable:

"The current input timing is not supported by the monitor display. Please change your input timing to 1920x1080@60Hz or any other monitor listed timing as per the monitor specifications."

Is there something that could be causing an incompatibility or is it likely to be just a dud cable?

Details: Ubuntu 10.10, Nvidia GeForce 8500 GT, Dell U2311H monitor.

Answer 1

I've tested again with a 2m dual-link cable and it works fine, so it looks like the cable is probably just too long (for the combination of graphics card and monitor).

http://www.playtool.com/pages/dvitrouble/dvitrouble.html#shortercable