> Mark, can you try commenting out _TestCondition and seeing if you can 
> still get it to hang?;

I removed the _TestCondition class entirely from test_multiprocessing, 
and did make test again.  It didn't hang! :-)  It crashed instead.  :-(
 
The output's below, in all its gory glory.  I can't make head or tail or 
it, but maybe someone else can.  The last two runs before this gave me a 
Segmentation fault.

test_multiprocessing
Debug memory block at address p=0x2ecd928:
Debug memory block at address p=0x2ecd928:
    49 bytes originally requested
    49 bytes originally requested
    The 4 pad bytes at p-4 are     The 4 pad bytes at p-4 are 
FORBIDDENBYTE, as expected.
FORBIDDENBYTE, as expected.
    The 4 pad bytes at tail=0x2ecd959 are     The 4 pad bytes at 
tail=0x2ecd959 are not all FORBIDDENBYTE (0xfb):
not all FORBIDDENBYTE (0xfb):
        at tail+0: 0x7d        at tail+0: 0x7d *** OUCH *** OUCH

        at tail+1: 0x74        at tail+1: 0x74 *** OUCH *** OUCH

        at tail+2: 0x71        at tail+2: 0x71 *** OUCH *** OUCH

        at tail+3: 0x02        at tail+3: 0x02 *** OUCH *** OUCH

    The block was made by call #782281511 to debug malloc/realloc.
    The block was made by call #782281511 to debug malloc/realloc.
    Data at p:    Data at p: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 ... ... 87 87 71 71 02 02 2e 2e 00 00 1c 1c 02 02 85 85

Fatal Python error: bad trailing pad byte
Fatal Python error: bad trailing pad byte
make: *** [test] Abort trap