0.6.4 game crash

[boltyhead]

I just had a game crash, I had an assembling plant selected and when I walked away it stayed selected, I tried the esc button aswell as Q and E to close it/switch to my inventory, my inventory aswell as the escape menu appeared on top of the assembling plant menu but they didn't cause the gui to disappear, when I went to select an item inside of the assembling plant is when I got the error.
I have never got this error before this time and I don't know if it was just a one time off error and not common but I thought I would share it here regardless, it doesn't occur after reloading and opening the assembling plant.

I am running Windows 7 64 bit and this game has been playing for a fair amount of time.

[kovarex]

I tried to reproduce, but without success, so I moved this to pending.