Hello mifi....
I had the same irritating problem here with my Ubuntu as well...even recompiling few times did not help.... the log files does not say much either....at times for me FG crashes the ENTIRE system...
and
Usually i realised just b4 FG crashes, the frame rate fells dramatically
To overcome, this is what i did...
1)Start FGRUN, on top left corner, select full screen mode with 800X600 display mode
2)Also change your bit rate from 32 bits to 24
3)Select you aircraft and go ahead with your game....
4)When you are in the game, go to View --> rendering
5)Now DISABLE shader and DISABLE 3d clouds
Now fly around... you will see that the frame rate improves dramatically...
And this has prevented some FG crashes lately
Now if this works for you as well, then what is the real problem initially?
Seems to me Display driver and FG may have some problems...
And/Or Malloc...memory allocations/kill problems?
these are just assumption
Anyway i Hope that helps.....