If you are running as a Windows user with administrator privileges, MYOB triggers a UAC prompt to ask for your permission to run as administrator. As the MYOB ODBC runs MYOB itself invisibly this is an issue as the UAT question would need an answer with each connection.
We do not recommend turning off the UAC. That does allow MYOB to work without the prompt but can be a security risk regarding stuff off the web you may not want to run and still does not make it work with the ODBC.
The following is specific to MYOB and does both get rid of UAC messages on MYOB and allow the ODBC to work:
Using Notepad or your favourite text editor go to the MYOB program folder and open Myob.exe.manifest (or for Premier and Enterprise versions Myobp.exe.manifest)