Bitcoin qt v0.8.2 and v0.8.3 crashing before it loads (mac)

Hello,

bitcoin-qt v0.8.2 wouldn't open on my mac yesterday, so I upgraded to v0.8.3 and am getting the same error as before. I'm not a computer programmer so it doesn't mean much to me. Here is the error message, which comes up in a "problem report" box. The report is quite lengthy and I don't want to post it all before I get some feedback. If anyone can help I would appreciate it.
Peace

Process: Bitcoin-Qt [296]
Path: /Applications/Bitcoin-Qt.app/Contents/MacOS/Bitcoin-Qt
Identifier: org.bitcoinfoundation.Bitcoin-Qt
Version: 0.8.3 (0.8.3)
Code Type: X86 (Native)
Parent Process: launchd [86]

Date/Time: 2013-08-14 10:15:10.557 +0900
OS Version: Mac OS X 10.6.8 (10K549)
Report Version: 6

Interval Since Last Report: 190116 sec
Crashes Since Last Report: 7
Per-App Interval Since Last Report: 325 sec
Per-App Crashes Since Last Report: 4
Anonymous UUID: 91DD2B25-533B-4FDB-A266-AD0FE18642AC

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Application Specific Information:
Assertion failed: (pfork != NULL), function SetBestChain, file src/main.cpp, line 1761.

Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libSystem.B.dylib     0x915bec5a __kill + 10
1 libSystem.B.dylib     0x915bec4c kill$UNIX2003 + 32
2 libSystem.B.dylib     0x916515a5 raise + 26
3 libSystem.B.dylib     0x916676e4 abort + 93
4 libSystem.B.dylib     0x9165420f __assert_rtn + 252
5 ...itcoinfoundation.Bitcoin-Qt   0x000d1d75 SetBestChain(CValidationState&, CBlockIndex*) + 3541
6 ...itcoinfoundation.Bitcoin-Qt   0x000d3538 ConnectBestBlock(CValidationState&) + 824
7 ...itcoinfoundation.Bitcoin-Qt   0x00125848 AppInit2(boost::thread_group&) + 22744
8 ...itcoinfoundation.Bitcoin-Qt   0x00022230 main + 7504
9 ...itcoinfoundation.Bitcoin-Qt   0x0001f501 start + 53

Thread 1: Dispatch queue: com.apple.libdispatch-manager
0 libSystem.B.dylib     0x91584382 kevent + 10
1 libSystem.B.dylib     0x91584a9c _dispatch_mgr_invoke + 215
2 libSystem.B.dylib     0x91583f59 _dispatch_queue_invoke + 163
3 libSystem.B.dylib     0x91583cfe _dispatch_worker_thread2 + 240
4 libSystem.B.dylib     0x91583781 _pthread_wqthread + 390
5 libSystem.B.dylib     0x915835c6 start_wqthread + 30

Thread 2: com.apple.CFSocket.private
0 libSystem.B.dylib     0x9157cac6 select$DARWIN_EXTSN + 10
1 com.apple.CoreFoundation    0x904a0c53 __CFSocketManager + 1091
2 libSystem.B.dylib     0x9158b259 _pthread_start + 345
3 libSystem.B.dylib     0x9158b0de thread_start + 34

Thread 3:
0 libSystem.B.dylib     0x9157cac6 select$DARWIN_EXTSN + 10
1 QtCore    0x019ffa90 qt_safe_select(int, fd_set*, fd_set*, fd_set*, timeval const*) + 320
2 QtCore    0x01a03dda QEventDispatcherUNIXPrivate::doSelect(QFlags<QEventLoop::ProcessEventsFlag>, timeval*) + 394
3 QtCore    0x01a0426f QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 175
4 QtCore    0x019cd471 QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 65
5 QtCore    0x019cd84a QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 314
6 QtCore    0x018aba45 QThread::exec() + 261
7 QtCore    0x018af0d3 QThread::terminate() + 787
8 libSystem.B.dylib     0x9158b259 _pthread_start + 345
9 libSystem.B.dylib     0x9158b0de thread_start + 34

Thread 4:
0 libSystem.B.dylib     0x9158baa2 __semwait_signal + 10
1 libSystem.B.dylib     0x9158b75e _pthread_cond_wait + 1191
2 libSystem.B.dylib     0x9158d3f8 pthread_cond_wait$UNIX2003 + 73
3 ...itcoinfoundation.Bitcoin-Qt   0x000aed52 boost::condition_variable::wait(boost::unique_lock<boost::mutex>&) + 354
4 ...itcoinfoundation.Bitcoin-Qt   0x0011428d CCheckQueue<CScriptCheck>::Loop(bool) + 413
5 ...itcoinfoundation.Bitcoin-Qt   0x000c3d93 ThreadScriptCheck() + 67
6 libboost_thread-mt.dylib    0x00ce8845 boost::detail::thread_data_base::~thread_data_base() + 779
7 libSystem.B.dylib     0x9158b259 _pthread_start + 345
8 libSystem.B.dylib     0x9158b0de thread_start + 34

Thread 5:
0 libSystem.B.dylib     0x91583412 __workq_kernreturn + 10
1 libSystem.B.dylib     0x915839a8 _pthread_wqthread + 941
2 libSystem.B.dylib     0x915835c6 start_wqthread + 30

Thread 0 crashed with X86 Thread State (32-bit):
eax: 0x00000000 ebx: 0x91667693 ecx: 0xbfffe23c edx: 0x915bec5a
edi: 0x000006e1 esi: 0x0032498b ebp: 0xbfffe258 esp: 0xbfffe23c
ss: 0x0000001f efl: 0x00200282 eip: 0x915bec5a cs: 0x00000007
ds: 0x0000001f es: 0x0000001f fs: 0x00000000 gs: 0x00000037
cr2: 0x9165158b