I'm working on getting xscreensaver running on 10.6, and roughly 2/3rds of the time any of the savers launch, they crash here:

Program received signal: "EXC_BAD_ACCESS".
#0 0x00007fff825df445 in +[NSLayoutManager(NSPrivate) _doSomeBackgroundLayout] ()
#1 0x00007fff825df23f in _NSPostBackgroundLayout ()
#2 0x00007fff84cfe437 in __CFRunLoopDoObservers ()
#3 0x00007fff84cda6e4 in __CFRunLoopRun ()
#4 0x00007fff84cda03f in CFRunLoopRunSpecific ()
#5 0x00007fff86e50c4e in RunCurrentEventLoopInMode ()
#6 0x00007fff86e50a53 in ReceiveNextEventCommon ()
#7 0x00007fff86e5090c in BlockUntilNextEventMatchingListInMode ()
#8 0x00007fff824a5570 in _DPSNextEvent ()
#9 0x00007fff824a4ed9 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
#10 0x00007fff8246ab29 in -[NSApplication run] ()
#11 0x00007fff82463844 in NSApplicationMain ()
#12 0x000000010000342c in main (argc=1, argv=0x7fff5fbff380) at /Users/jwz/src/xscreensaver/OSX/main.m:16

I'm not even using NSLayoutManager (as far as I know), so presumably this is some random memory corruption that happened somewhere else entirely, but turning on the MallocCheckHeap and related environment variables doesn't reveal anything. Any ideas how to debug this?

None of the XCode "Performance Tools" seem even remotely useful for tracking down memory corruption, but maybe I just don't understand them. Anyway, I thought the garbage collector was supposed to make everything sweetness and light?