In a 64 bit windows server operating system (Server 2008 R2), there are two ODBC managers.
When you pull up the usual menu for the ODBC / DSN system, it is for the 64 bit ODBC manager and 32 bit applications will not work using these DSN'S.
You will need to open the 32 bit ODBC manager on the 64 bit server to set the connections:
The executable can be found at this location: C:\Windows\SysWOW64\odbcad32.exe