Help! Fatal Error after update of Membership

I have had so many problems with the Membership plug in I was afraid to upgrade with the new version.

But, I went ahead and did it and now I have a fatal error and cannot access the site.

Fatal error: Cannot redeclare class twocheckout in /home/sisterh0/public_html/wp-content/plugins/membership/membershipincludes/gateways/gateway.twocheckout.php on line 9

Please help as this is a large membership site and my members will be e-mailing me.

Thanks,

JoAnn