membership plugin gives fatal error

I am getting this error:

Fatal error: Call to undefined method WP_User::WP_User() in mysite.com/newwp/wp-content/plugins/membership/membershipincludes/classes/class.membership.php on line 23

when I click Membership, Edit Members

I've attached a screen shot.

To the best of my ability to follow directions, I have completed the setup of the plugin and activated everything. With no error.

After getting the error, I can't click on my user name in the top right corner and get the dropdown box. Until I click another menu option i.e. away from the Membership, Edit Members screen.

I searched the forum and wondered if I could have installed previously using a different user name. The setup screens were vaguely familiar and I already had the correct categories. And I vaguely remember thinking this was more complication than I needed when I got to the drag and drop levels bit.

In any event this was a new install. Just to be sure I re-uploaded via FTP.

I checked the config file and the admin name was the one listed. I checked the "old" user profile and that user was not an administrator and the "This user has access to administer the Membership system." was not checked.

Oddly though when I looked at my admin user profile, instead of the "This user has access to administer the Membership system." I see the same fatal error as above.

I updated the "old" user profile, changed the config file and tried to use that user. SAME exact error on Edit Members and on the profile.

This is not my week to get wpmudev plugins working. I had a great run of it at first but nothing working for me this week.

Any ideas? I loathe the idea that I have to delete the database files and set this up again. Tedious.

Thanks
Lori