scripts in virtualenv hang indefinitely (python 3.

Question

I have previously used virtualenv with no problems under Python 2.7 and 3.5. Recently, I tried to create a new virtualenv and found that calling pip list caused an indefinite hang.

Calling any executable .exe in the virtualenv's scripts folder EXCEPT python causes an indefinite hang, which:

• can be broken out of by raising a KeyboardInterrupt (Ctrl-C), but provides no traceback (indicating that python has not yet started running the script?)
• but cannot be killed by "End Proccess" in the Task Manager

How do I even start to go about troubleshooting this? So far I have tried:

Successfully

• Activating and deactivating new virtualenv's
• Running pip, easy_install or virtualenv under the main python installation
• Trying to run a non-existing script under a new virtualenv (fails with command not found)
• Running python under a new virtualenv
• Running the python script files (.py) directly that pip, easy_install and wheel commands point to under a new virtualenv
• Running pip(.exe), easy_install(.exe) or wheel(.exe) under an existing, previously created virtualenv

Causes indefinite hang

• Running pip(.exe), easy_install(.exe) or wheel(.exe) under a new virtualenv
• Rolling back setuptools and virtualenv to known good versions (15.0 & 13.1) before creating a new virtualenv
• Uninstalling and reinstalling Python 3.5 before doing the above

The fact I can run the .py files directly leads me to believe that Windows is not handling the .exe execution correctly - any ideas on how I could reset, change or otherwise fix this?

It is worth noting that I noticed this after additionally installing Python 2.6, 3.3, and 3.4. I have since uninstalled these to try and get 3.5 working again.

Thoughts? I'm happy to provide log files if specifie