just started last week.... wont go off for anything. i figure ill check the fastener (havent done so yet) but i figured id post in case its a common problem with a common fix.

 

Probably an open in the wiring harness under the seat or a dirty connector.

 

at the part where you fasten it on to, wiggle it around w/ seatbelt fastened and see if it goes off, its probably just something there, my camaro did that for a couple days, but i would wiggle it around a little, and it would go off and on, until it finally just stayed off, that was prob 6+months ago,
goodluck

 

mines stayed on since i bought the car in 96?? till I buckles my belt.