Also, LTC mining requires more power due to increased VMEM usage. You must have pushed the PSU to it's limits.
So that is most likely the reason for your PSU failure
https://bitcointalksearch.org/topic/--91156
I played with worksize and aggression. Touching those setting usually optimize. I can't get the card to even start with reaper without a crash.
The difference between 300 memory and 800+ does take a toll. I'm guessing my PSU was at it's limit already. That's not to say that Reaper could REALLY use an update for efficiency. I'm thinking we'll be seeing a lot of those types of questions in the next few months.