Calzone 0 Newbie Poster

I have a Dell 2208WP monitor. It has worked fine until just recently when it started going straight into Power Save mode as soon as I press the power button on the PC, and it will not come out no matter what I do. PC is about 4-5 yrs old, athlon 3500+ with NV6800GT card, attached by DVI.
Symptoms and actions taken:
1. Monitor went into power save mode right from boot up. Did not see boot screen or anything. PC appears to be booting just fine - at least its making all the right noises!
2. Do not have a spare monitor to test the PC for isolation.
3. Do not have a spare pc to test the monitor.
4. Tried all three inputs, DVI, HDMI and VGA, all exactly the same.
5. Swapped dvi-d cable for dvi-i cable, screen worked until PC went into sleep, then monitor entered power save and has since not ever come out. Suggests a decaying part somewhere that has finally given up the ghost....
5. It was time for an upgrade anyway, so bought a HD5770 GPU and replaced - exactly the same - no screen.
6. monitor can clearly detect a signal because if I unplug the cable, it shows a test pattern - cable in, it goes straight into power save.
7. Replaced MObo battery (from another forum suggestion). Nada.
8. Options: monitor is broken - electronics behind the inputs not working properly - solution replace monitor, test: find another computer to test it with.
9.Options: PC power supply knackered and not providing enough power to drive GPU card. Test: another monitor on GPU (maybe it might work anyway); or if montor works on another PC its the PC - solution: replace PSU and or MOBO.

Anyone have any other ideas? The above tests/solutions look expensive to me!! already £130 down on new GPU and still no screen!! Becoming slightly jarring....

Cheers for any advice.

Calzone