That test works for me on this x86_64 Fedora 13 box (using latest 2.7 code from SVN, built and installed to a test prefix):

[david@surprise bin]$ ./python -m test.regrtest -v test_subprocess
== CPython 2.7.1+ (release27-maint:87724, Jan 3 2011, 19:39:26) [GCC 4.4.4 20100630 (Red Hat 4.4.4-10)]
==   Linux-2.6.33.3-84.fc13.x86_64-x86_64-with-fedora-13-Goddard little-endian
==   /tmp/test_python_24104
Testing with flags: sys.flags(debug=0, py3k_warning=0, division_warning=0, division_new=0, inspect=0, interactive=0, optimize=0, dont_write_bytecode=0, no_user_site=0, no_site=0, ignore_environment=0, tabcheck=0, verbose=0, unicode=0, bytes_warning=0)
test_subprocess
...
test_executable_without_cwd (test.test_subprocess.ProcessTestCase) ... ok
...
test_executable_without_cwd (test.test_subprocess.ProcessTestCaseNoPoll) ... ok
...

though I do see another failure:
======================================================================
FAIL: test_wait_when_sigchild_ignored (test.test_subprocess.POSIXProcessTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/david/coding/python-svn-anon/2.7-clean/tmp-prefix/lib/python2.7/test/test_subprocess.py", line 841, in test_wait_when_sigchild_ignored
    " non-zero with this error:\n%s" % stderr)
AssertionError: sigchild_ignore.py exited non-zero with this error:
/home/david/coding/python-svn-anon/2.7-clean/tmp-prefix/bin/python: can't open file 'subprocessdata/sigchild_ignore.py': [Errno 2] No such file or directory


----------------------------------------------------------------------
Ran 123 tests in 17.621s

FAILED (failures=1, skipped=14)