I might have provoked that myself.
I started around Normen's area and wanted to get back to my own plot, which is pretty far from the main area. So, I used the "don't have to use the W key to move forward bug" (which is: hit TAB while holding W, you'll continue to walk. Even after closing the menu). Then I held SHIFT to run, and pretty much held the jump button too (SPACE). Loading stuff happened a couple of times but I guess at one point it tried to load while it was already loading? Or something similar. Anyway, got to around 2 FPS (w/ FRAPS), nothing happened... ALT-TAB to desktop to check if Mythruna was still "running", it wasn't. Then the game closed by itself.
As a result, I've got several dump files:
client.log
client-1.log
error-1317266905012.log
The first is 2679 KB
Second is 2 KB
Third is: 3424 KB
I obviously won't paste the 2 huge files in here...
client-1.log doesn't have much. No crash info that I see. Only a nifty warning about missing popup sound. Everyone using jME3 has that I imagine.
So, shall I zip those and attach them here (if they fit after being compressed) or would you prefer if I pasted only certain portions? It's your call.
Btw, I was trying to reproduce something, could be a serious issue but unsure right now, but unfortunately I couldn't get that behavior to happen again.