I agree with matthiaskrgr.

I also encountered this problem and had to use "kill -kill [PID]", since even
"kill [PID]" didn't work.
I'd  started the game in window mode and the "[X]" of the window didn't do a
thing, too - like matthiaskrgr wrote about [Esc].

I used a savegame from r5061 and another one from r5077 with freedroid being at
r5118.

I tried it another time and had to click approximately 103 times - each
producing the following output:
----------------------------------------------------------------------
Freedroid has encountered a problem:
In function: read_melee_shot.
FreedroidRPG package and version number: freedroidrpg 0.14.1+svn.
Field "time_to_hit" not found
The problem mentioned above is not fatal, we continue the execution.
----------------------------------------------------------------------

The next click killed the game:
----------------------------------------------------------------------
Freedroid has encountered a problem:
In function: ResolveMapLabelOnShip.
FreedroidRPG package and version number: freedroidrpg 0.14.1+svn.
Resolving map label SwitchOffLaserTrapMSOLobby-1 failed on the complete ship!
This is a severe error in the game data of Freedroid.

The questions coming up:
1. Is the game playable, when the savegame misses the field "time_to_hit" (for
all melee_shots)? If not, this error should be fatal.

2. Is there a reasonable way to unite non-fatal warnings of the same type - i.e.
to prevent the game from display a warning about one melee shot does not have
the field "time_to_hit" if this warning already has been displayed once (for
another melee_shot).
In the case of my example, the game should have warned me ONCE (not 103 times)
because of the missing "time_to_hit" fields and then instantly* having crashed
because of the missing label.

* instantly means without further clicking.