I posted this in the plug in support area but haven't received a reply yet so I'll try here :)
I receive a 500 error when attempting to use the Groups plug in. It activates, but when I click on settings to configure it I get the error.
I followed the work around instructions involving removing and reinstalling the plug in offered by another poster, but got the same error regardless.
I attempted to enable DEV_MODE in order to generate a specific error to report but when I did that my site didn't load at all.
I replaced the config.php file with the back up one I saved before hand, so my site loads again, however I am back to square one.