Well, I have very bad experiences of warranties, I unlocked some pipes on an X800GTO and i think one of the memory chips failed, and wouldnt boot, and Sapphire said they wouldnt refund, although my dad phoned and had an argument and they refunded me the lot, although yeh i was awfully close to loosing £170.
Did you tell them exactly what happened, like the truth. That was dumb and thats why they refused. You just tell them I went to boot one day and I smelled smoke and when I opened case I noticed it was burnt or w/e.