Tim,
Many people say it's not heat, but most of the time in OFF support cases so far, it is. May not be here, of course, but at least we have to check into that.
If other games are fine then means nothing. OFF stretches your CPU a lot, and memory, and GPU memory. If there is anything that will find it out, OFF will.
I have been doing PC tech support at one level or another for around 17 years, and flight simming for 25 too so I think we all know one or two things ;).
Recently I too had crashes in OFF never had them before, couldn't work it out.. opened my well ventilated case, found my 8GB of super duper amazing super cooled OCZ RAM with heat pipes.... melted the heatpipes off !!! Yep the cooler was 45 degrees angled to the memory. Nice.
The weren't even overclocked.. so much for paying extra for the "good" stuff.
So never say never is my motto.
What sliders are you set to?
Did you read through the FAQ Q.25 and try anything at all of those 7 things to try?
First thing I'd try is running cfs3config and reset to default? Then put your slider settings back in.
Did you install any other software recently? Any other new drivers?
It could also be the craft you are flying is different to the norm, the location, the date, with different events happening, anything really. Could be drive corruption (did you do a Scandisk?)
By the way no need to PM me to visit the thread, I visit often, but it is 12.30 am here so wanted a break :)