I used the steps above to cause the crash to happen in the debugger. It looks like an explicit assert or somesuch in canleadtransunit(). Here's the backtrace:
0x9003ddac in kill ()
(gdb) bt
#0 0x9003ddac in kill ()
#1 0x9010ffdf in raise ()
#2 0x9010eb32 in abort ()
#3 0x0008d0af in bug ()
#4 0x000930ea in canleadtransunit ()
#5 0x0009ba47 in transferunits ()
#6 0x000a4fd7 in viewland ()
#7 0x000a9b53 in playplayerturn ()
#8 0x000aa574 in playturn ()
#9 0x0005be85 in start ()
#10 0x00090d8f in SDL_main ()
#11 0x00002262 in -[SDLMain applicationDidFinishLaunching:] ()
#12 0x927e617b in _nsnote_callback ()
#13 0x908553e6 in __CFXNotificationPost ()
#14 0x9084cbd1 in _CFXNotificationPostNotification ()
#15 0x927de724 in -[NSNotificationCenter postNotificationName

bject:userInfo:] ()
#16 0x927e56c9 in -[NSNotificationCenter postNotificationName

bject:] ()
#17 0x93284e94 in -[NSApplication _postDidFinishNotification] ()
#18 0x93284d7e in -[NSApplication _sendFinishLaunchingNotification] ()
#19 0x9328487d in -[NSApplication(NSAppleEventHandling) _handleAEOpen:] ()
#20 0x93284448 in -[NSApplication(NSAppleEventHandling) _handleCoreEvent:withReplyEvent:] ()
#21 0x927ebe65 in -[NSAppleEventManager dispatchRawAppleEvent:withRawReply:handlerRefCon:] ()
#22 0x927ebc8f in _NSAppleEventManagerGenericHandler ()
#23 0x91518fb5 in aeDispatchAppleEvent ()
#24 0x91518ee6 in dispatchEventAndSendReply ()
#25 0x91518db2 in aeProcessAppleEvent ()
#26 0x92ddf0e4 in AEProcessAppleEvent ()
#27 0x9328263d in _DPSNextEvent ()
#28 0x93282056 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
#29 0x9327bddb in -[NSApplication run] ()
#30 0x00002922 in main ()
Hope that helps.
-p