I tried to make a backtrace as described on
http://www.freedroid.org/pmwiki/pmwiki.php?n=Doc.BackTraces, but I'm not sure
this is helping. I'm not familiar with gdb or C(++).

...lots of those...
[New Thread 0xb4f99b40 (LWP 32176)]
[Thread 0xb4f99b40 (LWP 32176) exited]
[New Thread 0xb4f99b40 (LWP 32177)]
[Thread 0xb4f99b40 (LWP 32177) exited]

Program received signal SIGFPE, Arithmetic exception.
0x080a14f8 in update_light_list ()
(gdb) bt full
#0  0x080a14f8 in update_light_list ()
No symbol table info available.
#1  0x08099f2b in AssembleCombatPicture ()
No symbol table info available.
#2  0x08091df6 in Game ()
No symbol table info available.
#3  0x08059961 in main ()
No symbol table info available.
(gdb) 

I'm now reasonably sure that this bug can be reproduced by moving south as far
as possible and then east through the corridor. At the end of the corridor, the
game crashes. (see map ;)