For 2.6.4 I get a test_float failure on Solaris as well:

test test_float failed -- Traceback (most recent call last):
 File "/home/tuba/skipm/src/python/Python-2.6.4/Lib/test/test_float.py",
line 765, in test_roundtrip
   self.identical(-x, roundtrip(-x))
 File "/home/tuba/skipm/src/python/Python-2.6.4/Lib/test/test_float.py",
line 375, in identical
   self.fail('%r not identical to %r' % (x, y))
AssertionError: -0.0 not identical to 0.0

Haven't looked at 2.7 or 3.1 yet, but it seems to fall into the same
class of test failures as the tanh(-0.0) critter.