Resolution Problems

I've been running Guild Wars for almost a year now on my current computer at 1600x1200, 85hz (my monitors optimal settings) and I've had no problems whatsoever. Today I went to open Guild Wars my monitor blacked out and a red text box came up saying:

SIGNAL FREQUENCY IS OUT OF RANGE
FH > 106.4khz
FV > 85.2hz
PLEASE CHANGE SIGNAL TIMING

After trying many to figure out how to bypass it to get to the settings and also trying to create an nVidia profile to alleviate the problem, I just deleted gw.dat and started over. I can use any resolution up to, but not including, 1600x1200 on any frequency. Here's my computer's specs:

Windows XP Professional Service Pack 2
AMD Athlon XP 2600+
1Gb RAM
Directx v9.0c
NVIDIA GeForce FX 5900XT

Any help would be greatly appreciated

I'm almost certain its the monitor, I get the exact same issue when I change my screen size (at any time) higher than 1280 x 1024. Have you tryed this on any other monitor? Say for instance a friend who has a new(er) monitor?

/edit - typo

Nah, I don't really have access to a newer monitor to test this. However my desktop display settings can be run at 1600x1200 and up without a problem.

I just tried running half life 2 and I'm getting the same problem. I don't understand how something like this could happen literally overnight.

edit: my monitor is a NEC FE990 and I was checking the settings. Looks like the frequency settings changed to 60 hz default. Also looks like the drivers for my monitor disappeared. I'm gonna fool around with the drivers a bit see if that's the problem.

edit2: I can't seem to get the drivers to work. It's like Windows just doesn't want them or something. Any help?

Don't know why but it seems my vid card drivers went all wiggy and stopped detecting the monitor as it was supposed to. It was being registered as Default Monitor instead of NEC MultiSync FE990 and was severely limited in terms of refresh rates. So I just reinstalled the forceware drivers, rebooted, and bingo, Guild Wars looks pretty again

Nice, grats. Glad you figured it out w/o too much aggervation ^_^