Power Mac G5 DVI Connection Issues

When connecting an Optiquest Q22wb Monitor to my Power Mac G5 using a DVI-D cable, there is an intermittent problem where the computer will lock (either sleeping or going to screensaver), and when I wake the computer, I see the usual unlock screen, however when unlocking it I am presented with a black screen.

If I select "switch user" instead, I see the normal user login window. It seems anytime I try to access my user profile, the screen is black.
The only solution I have at the moment is to restart my computer.

This issue does not exist if I use a VGA cable from the monitor, to the adapter for the Power Mac.

Here are the specs.

Computer Specs:

Model Name: Power Mac G5
Model Identifier: PowerMac7,3
Processor Name: PowerPC G5 (3.0)
Processor Speed: 2 GHz
Number Of CPUs: 2

ATI Radeon 9600:

Chipset Model: ATY,RV351
Type: Display
Bus: AGP
Slot: SLOT-1
VRAM (Total): 128 MB
Vendor: ATI (0x1002)
Device ID: 0x4150
Revision ID: 0x0000
ROM Revision: 113-A58504-113
Displays:
Q22wb:
Resolution: 1680 x 1050 @ 60 Hz
Depth: 32-Bit Color
Core Image: Hardware Accelerated
Main Display: Yes
Mirror: Off
Online: Yes
Quartz Extreme: Supported
Rotation: Supported
Display Connector:
Status: No Display Connected


Any input would be helpful!
(Please don't tell me to just use a VGA cable...)

Well I wo't tell you that then.......................

Hmm this is a stumper. Can you try dropping your resolution and test again and see if that has any change? Try this with your DVI connection.