Thanks, sorin.  This issue is at least affected by the fix to issue 2304.  I don't currently have an up-to-date version of 2.7 trunk on my windows VM, so I can't test your code there.  (Note that 'import tee' needs to be removed before your test program will run.)  Adding Tim and Brian to nosy so they can check it out.  It is quite possible (even likely) that 2304 fixed this problem as well.