Setup:

Main server = 10.6.8 client

Secondary server = 10.7.3 client

Both bound to OD on 10.6.3 Server

Confirmed group and user on OD from both servers and a client machine using:

sudo dsmemberutil checkmembership -u 1234 -g 5678

I received the response "user is a member of the group" from all three machines

I check the group name spelling in the .fp7 file that it matched the OD

Account status is active

Access via FileMaker Network (fmapp) is checked under extended privileges.

Under Configuaration: Database sever : Security: Client Authentication radio button has FileMaker and external server accounts selected and saved.

The file that won't open with external auth will open with a FileMaker account.

The file contains TOs that point to both servers.

The file resides on the secondary server.

These servers do not engage in any syncing.

What am I missing?

Lion OS has likely broken External Authentication. There have been some reports of this.

Steven

So my only choice is to go back to Snow Leopard?

Be sure you're using the short names all the way around. Also, can you swap roles of the servers? Or swap the files?

Steven