Certain monitoring (and at least one zenpack) needs to use twisted.internet.ssl, which depends on pyopenssl.  Running

python -c "import twisted.internet.ssl"

as the zenoss user should produce no output.  If it says

ImportError: No module named OpenSSL

You will need to install the module.  As the zenoss user, download and install the pyopenssl package:

1. Download pyopenssl (probably hosted at pypi)
2. untar pyopenssl into any directory and enter that directory
3. run ./setup.py install AS THE ZENOSS USER
4. before testing that it worked, it is important to move out of that directory; it might interfere.