BIG PROB: System enters standby/suspend mode

1½ years ago (summer 2000) I decided to upgrade my system from a P3/500 to an Athlon 1 ghz, and being the top mobo at the time (according to everyone I asked, at least), the choice fell on the Asus A7V as a platform.

After being through all the crap with 4-in-1's, AGP fixes and BIOS updates, I got myself a system running quickly and stably on Windows 2000 Professional. Until one day, the system would start entering standby mode (called suspend mode in the manual, green power LED flashing) on its own. It would do this sometimes after hours, sometimes seconds after power-UP. It would never happen before POST, but sometimes when I was in the BIOS tinkering. No event log/error log messages - when the computer ran, it ran perfectly. My system specs (see sig) were the same then as today, except I was using cheapo 2x128 mb PC100 SDRAM and a TNT2 Ultra AGP 4x graphics card.

One day, the problem disappeared. Woohoo! I thought, and kept using the computer as before, now sans sudden shutdowns. Months later (about 2 months from today) I decided to upgrade to Windows XP, which went flawlessly, I've not needed VIA 4-in-1's or AGP fixes and everything's been running well.

Last week, I moved the computer from one place to another, and the problems re-appeared. First, it would happen whenever the table the chassis stood on, or the chassis itself, was shaken or hit a little - lifting my keyboard up an inch and dropping it back down would trigger entry into standby mode, knocking lightly on the side of the chassis would, too.

When I say "standby mode" I mean: System shuts down, monitor goes into standby, green power LED is blinking. Pressing the power button will NOT power up the system. Pulling the power cord, waiting until the blinking stops, and then powering up again, will. Holding the power button for 4 secs also stops the blinking, and allows the system to be powered back on as well.

Power management is disabled in BIOS, as is standby mode and all other power management functions are turned off.

Later the same week, I moved the system back to its original location, hoping this would clear the problem. It didn't - instead, the shutdowns now seem completely random, shaking or no shaking. Needless to say, it's getting on my nerves, as the system has never been able to stay on for more than 45 minutes or so. Still nothing in any event logs, Windows XP when booted up acts just like it was shut down normally, no errors, no warnings, no scandisk.

Last time I had these problems, I thought it was the PSU's fault, as it's a dirt cheap Macron 300W - but how would the PSU cause the motherboard to think it's supposed to enter standby mode when standby mode (suspend) is disabled in BIOS?

If anyone can help, please do. I'm going nuts over this! If I can't figure this out (or it goes away again) I will be forced to get a totally new mobo AND psu - a surefire way to solve the problem, but a bit too costly for comfort.

Thank you in advance. My full system specs follow:

A7V, 1.02 pcb, Bios: 1008
Athlon T-Bird 201FSB @ 1.01GHz, TaiSol OEM fan, No OC
1x256MB PC133 SDRAM CSL2
Normal temps: CPU 45-50 C, mobo 30-35 C
Voltages: VCORE 1.77V, +3.3 3.48V, +5 4.99V, +12 11.91V

Promise Ultra100 P/M: IBM Deskstar 75GXP ATA100
Promise Ultra100 P/S: IBM Deskstar 22GXP ATA66
VIA Primary IDE master: Pioneer DVD-ROM 16x ATA66
VIA Primary IDE slave: HP CD-Writer 9310i 10x ATA66
AGP : Absolute 3d Power Morpheus Geforce3
PCI3: SB Live! Value
PCI5: 3com Etherlink 3XP 10/100

KEYB: Keytronic MPR-2 (generic)
MOUSE: Microsoft Intellimouse Explorer USB

CASE: Coolermaster ATCS-200 ATX miditower
PSU: Macron MPT-301 300W ATX
OS: Windows XP Professional

I have 2 possible explanations for this:
1. You could have a bad PSU, but then you should always got htis problem and not suddenly after a couple of months.
2. Maybe something inside your case (especially your mobo) is shorting. Check if your mobo is seated properly and if all connectors are plugged-in properly.

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I'd be willing to bet that the power switch on the front of your case is defective. Or maybe there is a bare spot in the leads to it that are intermittently shorting inside the case somewhere.

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