Last year I bought a used Phillips 190S 19" LCD monitor via ebay. Hooked it up to my HP DC7100 loaded to dual boot XP Pro Sp3 or PCLinuxOS. But before I could hook it up, I had to do a little re-forming of a damaged (partially crushed) connector on the SVGA cable. That accomplished, and I was off to happy camperland. For nearly a year.

Last week it began intermittently misbehaving at startup. When I power up the computer, the monitor power LED goes from amber (sleep) to green (on) and the display presents... ordinarily. But now, the monitor power LED goes from amber to green for less than a second before it reverts back to amber. <--That cycle would then repeat continuously at about 3 - 4 second regular INTERVALS. The result is that I am presented with an intermittant & unuseable video display.

Online or off.
Reboot.
Disconnect power cords: computer AND monitor
Bought and installed a new SVGA cable
Swapped computers to a Compaq loaded with W2KPro
Swapped monitors to a 15" Dell LCD
Swapped computers back to the HP

1. BOTH computer/monitor COMBINATIONS presented the same symptoms.
2. BOTH computer/monitor combinations with different cables presented the same.
3. I managed to reaquire useable video only after dragging out an old Gateway 2000 CRT monitor.

Item: My gut tells me it's asking too MUCH of coincidence to condemn both SVGA cables. It also tells me it's asking too much of coincidence to condemn both LCD monitors. That said, I have to admit to the fact that so far I've yet been able to achieve success with the new cable. But I HAD achieved success with the original cable.

Item: Neither computer has a removeable video card.

I'm stumped.

Can video drivers go corrupt from outta the blue? And if so, wouldn't said corrupt drivers also botch the display on a CRT monitor?Simple.
All computers can display a on a any VGA compatible monitor without drivers
Boot in SAFE mode with VGA. No driver issue.

Cables WEAR out. They never self heal.
Monitors can be erratic. The never get lastingly better.
Dammaged connectors give trouble.
It is not Karma.
It is the cost of ownership.   

Put it this way. How do you like to fly on an airplane that is forty years old and the skin is peeling off?
I would try to "borrow" a video card and then run through your tests on the 2 monitors (using the card in the 2 computers if possible) truenorth