I had this problem also and found that I had two cookies for our boards. One has named "cgi-bin" (after the directory where Threads is installed - yours my be different) and the other was named the full URL of the boards. As it turns out the "cgi-bin" cookie was set from an older version of Threads before the "path" variable was added. Deleting the "cgi-bin" cookie solved the problem. Let me know if this fixes your problem and I will post the hack I used to fix for all of our board users.
