I don't know whether this really the same origin, but there is
a longstanding problem which makes the selftest of Python-2.4
hang infinitely.
There is a test which checks signal delivery. It doesn't use threads
itself. If I execute it separately, it succeeds without problems. If
I execute it within the whole selftest suite, it hangs in "sawait"
forever.
There is quite a number of other tests in the suite executed before
that signal check, one of them activating the thread subsystem.

Sorry that I didn't track it down further yet, but this is a
complex matter and the state of debugging support for threaded
programs doesn't make it easier.

It can be simply reproduced:
$ python2.4
[...]
>>> from test import autotest
[proceeds until]
test_signal
[hangs]

best regards
Matthias