My Ti4200 broke in a very very strange way...help?

Hi all.

Recently, my Leadtek GF4 Ti4200 64MB stopped working. Whereas it used
to work fine in my Shuttle PC (the Nforce2 based SN41G2), recently
when I removed the card (to clean dust off the heatsink fan) and put
it back in, the Shuttle motherboard's 'AGP Protection LED' went on.

After reading the manual, I found that this LED lights when the
motherboard thinks you have a older 3.3V card in its 1.5V-only AGP
slot -- it won't let you power up the machine in that state. Puzzled,
I put it in another Nforce2 motherboard. Same thing: AGP protection
LED on, no POST. Interestingly, the LED on that other mobo stayed on
_even after the card was removed_. That other motherboard now works
with its original card, but the LED remains on. I dont know if that's
relevant, but it's odd.

Now, I know that my Shuttle motherboard and its AGP are fine because

1) I can run the Shuttle perfectly with the onboard video, and

2) Another Gainward GF4 Ti4200 works in the same AGP slot.

Coincidentally, I bought this card EXACTLY one year ago, on October
25th. This means that the warranty seems to have run out, and my email
to Leadtek support has gone unanswered for 2 or 3 days.

Does anyone have ANY clue whatsoever about this? What went wrong, and
is there anything at all I can do to fix it?

Any suggestions appreciated!