Quickbooks Error -6190, -816 trying to open QBW file simultaneously from two computers via Server

Running QuickBooks 2009 Premiere Contractor edition.
QuickBooks file hosted on a Windows 2003 Server
2 Client machines running XP Home.
Like many others, I am getting "unable to open the company file" message with error (-6190 -816) when another computer already has the file open.

My Company QBW file is hosted by a server with only the QuickBooks Database Server Manager running on the server.
I have two machines using the company file - both have Hosting set to OFF.
Both client machines can open the Company file independently, so I don't think there are any firewall/network issues.
But they both get the same error when the other machine already has the file open.
I have followed instructions in other threads; deleting the Transaction log file on the Server, deleting the ND file on the server, restarting the QuickBooksDB19 and QBFCMonitorService on the Server, and rebooting the Server.

Thanks for reading!
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samsteridConnect With a Mentor Author Commented:
I finally got access to my Company QBW file on the server from 2 desktops simultaneously.  The "solution" was to give up on only having the Database Server Manager installed on the server.

It only started working after I installed the full version of Quickbooks 2009 on the server and chose Multi-User mode.  Then the ND file changed and finally listed the IP address of the server and changed the ServerMode = 1 to ServerMode=2.

When only the Database Server Manager was installed the ND file had very minimal info listed and always had ServerMode=1.  IF ServerMode=1 means Single-User Mode, I don't understand why or how that could get set with only the Database Server Manager installed.

Here's the best troubleshooting thread I found in my search:

I also followed the advice for Firewall settings here:

Even after I had it all working the first time, the Server file somehow got switched back to Single-User mode and I had to choose Muti-User from the main Quickbooks program on the server - again.

After many many hours on the phone with Intuit.... drum roll please ... took mcafee off the server and wala.

I also had to install the full version of Quicken on the server, but it still didn't work until mcafee was removed.
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