Membership crashed Admin

I am trying to install the Membership plugin on the WordPress/Buddypress site I’m developing here:

However, once I upload the plugin within WordPress and click Activate, I get: Server error

The website encountered an error while retrieving It may be down for maintenance or configured incorrectly.

Here are some suggestions:

Reload this webpage later.

HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

I am unable to connect to the admin at all (front end is all fine).

Once I delete the plugin, all is well. I then tried uploading the plugin via ftp – but as soon as it is uploaded, back to the error. Delete the plugin, all is well. What the heck?