Dynamics GP - Data Connection is blank after installing client on 64 bit machine

The machine is a 64 bit machine, and the Dynamics GP install does not create a 64-bit odbc connection.

You have to manually create a 32-bit odbc data connection for GP.

The 32-bit version of the Odbcad32.exe file is located in the %systemdrive%\Windows\SysWoW64 folder.
Run it and create your odbc.
Connect to your sql server using sa
untick all checkboxes on all windows as you go through the setup
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You should see your data connection when you run GP.

http://support.microsoft.com/kb/942976