GTX560 Ti overheated to plus 100c

Can anyone think why my card went crazy and totally overheated to over 100c, I was just about to start crysis and noticed the on screen display reading 102c and thought it was a faulty reading until it crashed and touched the card nearly burning my fingers
Yesterday I took card apart as it was reading around high 60s to replace the thermal compound as it had been there for ages put it all back correctly all connectors connected with no issues using it normally on web etc then this happens
As I'm obviously going to need a new card I want to make sure this is a one off and not fry a new card ???

I know it's over a year old year anyway

Might wanna check the warranty, example: Evga, you can take the heatsink off and replace the paste or the entire cooler. Warranty is still good as long as you can reassemble the card with factory cooler b4 sending it in.
One possible reason for what happened to your card would be dust built up in the heatsink/fan. I had an old 8600 GTS that I neglected to clean for a year or 2 when I noticed temps hitting 80c+, after blowing the dust out with compressed air temps dropped down to the 30-40c range.

Normally hits 73 under load
Everything was dust free as I had it apart the day before and new paste put down

It sounds like it didn't happen until you took it apart.

Just a thought, i think the heatsink isnt seated properly. Make sure you tighten the screws down alternately, and not to tight as that could warp the board. Alternately= in an X fashion. Good luck