Organic Groups subscription notifications are being sent to *all* group members instead of just group manager

There seems to be two OG/Notify-related problems on my 4.6.0 site:

1. Group subscription requests are going to all group members instead of just the group manager. Here's a copy of notification message (real names/email addresses obfuscated):
   

   From: webmaster@mymobilexchange.com
   [mailto:webmaster@mymobilexchange.com]
   Sent: Wednesday, April 27, 2005 8:37 AM
   To: Smith, John; firstname.lastname@mymobilexchange.net; Goliath, David; Barrymore, Drew; David, Larry; Markie, Mark; rad@mobiliq.com; Boy, Rich; Martin, Steve; Nugent, Ted; Thom, Tom; John, Wayne
   Subject: Subscription request for 'Powderstorm' from 'wannabee'

   You may approve or deny this request at http://www.MyMobileXchange.com/og/approve/1/9

2. The following error is then generated whenever a group member clicks the Approve/Deny link :
   

   Fatal error: Duplicate entry '887e2535987f9eea7c4ab8b0071c3d7b' for key 1 query: INSERT INTO sessions (sid, uid, hostname, timestamp) VALUES ('887e2535987f9eea7c4ab8b0071c3d7b', 0, '67.92.64.91', 1114778895) in /...myhostpath.../includes/database.mysql.inc on line 66

This error may be caused by the Organic Groups module so I have also filed a bug report with the OG project. I am marking this as critical because the problem is undermining user confidence into the security and stability of the system.