I have a BenQ XL2411Z monitor which has been used almost exclusively over the DVI connector and which just recently stopped working correctly at any other resolution besides 640x480 over the DVI connection. Connecting an HDMI cable or VGA cable allows the monitor to display at full resolution.
My current assumption is this is a hardware fault, but any software solutions or configuration/driver related suggestions would be welcome.
Sorry to hear about that. Has anything else in your setup changed? New graphics card? Adapter now being used? And have you tried a different DVI-DL cable?
Could you tell us how many monitors you are running and their Hz rate and resolution?
Is your “display mode” in the OSD monitor menu set to full?
It could be this. http://ask-leo.com/why_is_640x480_my_only_resolution_option.html
You might need to run DDU. (Display Driver Uninstaller) Please make sure you have the latest functioning drivers downloaded before you run the program.