Our team is having the same problem. Two of our games posted on FGL for review before the bidding process starts were denied on the grounds that it wasn't running on the newest OSX Mountain Lion with the newest Safari (HTML5 export).
I'm not currently up to the same os version as that or Safari version, but I had some helpful insight from a developer on site. Here's some of the stack reports:
1 ??? 0x0000000109861000 0 + 4454748160
4 com.apple.WebCore 0x0000000108517b11 WebCore::JSCallbackData::invokeCallback(JSC::JSValue, JSC::MarkedArgumentBuffer&, bool*) + 593
5 com.apple.WebCore 0x00000001085d3c73 WebCore::JSRequestAnimationFrameCallback::handleEvent(unsigned long long) + 275
6 com.apple.WebCore 0x0000000108771feb WebCore::ScriptedAnimationController::serviceScriptedAnimations(unsigned long long) + 187
7 com.apple.WebCore 0x00000001082d704d WebCore::DisplayRefreshMonitor::notifyClients() + 93
We've both tested this in other versions of Safari and Chrome, in Windows and OSX with no luck in reproducing this. Maybe the above info could help, but I honestly think it's Safari being a chump.