Quoting Bruce Whealton brucewhealton@yahoo.com:
Error message>>> Fatal error: Duplicate entry '0' for key 2 query: INSERT INTO sessions (sid, uid, hostname, timestamp) VALUES ('8cbce4316d9b4797ef37e81fee84a52f', 0, '68.213.148.90', 1168370359) in /home/brucew/public_html/home/includes/database.mysql.inc on line 66
My guess after looking at the system.install file for version 5 is that you already have the sid stored in the DB sessions table. The sid is the primary key and is the second key added to the table. There are no other unique keys identified.
Earnie