In the Plugin Configuration, do you have the auxiliary encoder checked? e.g. MPG1 = A and the aux check box.
Also, try running the plugin without the MPG configured. Set MPG1, MPG2, and MPG3 to -1. And uncheck any aux check boxes. This should disable any MPG code and then we can see if you are still getting the "Galil error 46 Gear axis both Master and follower" error.
And while you are in the Plugin config, enable the debug output check box. This creates a GalilDebug.txt file in the PlugIns directory. Then restart Mach and try to connect. If you get the error 46, exit mach and send me the GalilDebug.txt file at smurph@smcomp.com
Steve
Steve