Why does this simple NSWindow creation code trigger an autorelease pool crash on shutdown under ARC?

I am having an issue with an autorelease pool crash on shutdown which I've reduced to the small test case below that simply creates a window and then closes it. The crash disappears if the -fobjc-arc flag is taken away. Running on OS X 10.8.2, Clang 4.1 (421.11.66). I am hoping that someone with a more in depth understanding of ARC can enlighten me as to what is going on here - running with zombie objects on shows that it is the NSWindow object that is getting released too many times, or not retained enough, but I thought ARC was meant to take care of all this?

The stack trace is:

0   libobjc.A.dylib                 0x00007fff8fad4f5e objc_release + 14
1   libobjc.A.dylib                 0x00007fff8fad4230 (anonymous namespace)::AutoreleasePoolPage::pop(void*) + 464
2   com.apple.CoreFoundation        0x00007fff99d22342 _CFAutoreleasePoolPop + 34
3   com.apple.Foundation            0x00007fff936e84fa -[NSAutoreleasePool drain] + 154
4   com.apple.Foundation            0x00007fff936effa0 _NSAppleEventManagerGenericHandler + 125
5   com.apple.AE                    0x00007fff93a5ab48 aeDispatchAppleEvent(AEDesc const*, AEDesc*, unsigned int, unsigned char*) + 307
6   com.apple.AE                    0x00007fff93a5a9a9 dispatchEventAndSendReply(AEDesc const*, AEDesc*) + 37
7   com.apple.AE                    0x00007fff93a5a869 aeProcessAppleEvent + 318
8   com.apple.HIToolbox             0x00007fff8d0c18e9 AEProcessAppleEvent + 100
9   com.apple.AppKit                0x00007fff8e95c916 _DPSNextEvent + 1456
10  com.apple.AppKit                0x00007fff8e95bed2 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 128
11  com.apple.AppKit                0x00007fff8e953283 -[NSApplication run] + 517
12  Test                            0x00000001070e1d68 main + 152 (Test.mm:31)
13  libdyld.dylib                   0x00007fff8e10c7e1 start + 1

And the code for the test case is:

// Tested wi