Paul,
As I have pointed out in several threads before, double clicking on a mframe file does not work in OS X. Sometimes it launches VE Pro resulting in an invalid file error message, sometimes it launches VE Pro Server and doesn't load a file. There is no apparent distinction between mfram32 files and mframe64 files for the purpose of which program is launched.
To verify this, please do the following: Launch VE Pro Server (64-bit). Add an instance or two. Save the mframe64 file to your desktop. Now do the same with VE Pro Server and save the mframe32 file. Exit both programs. Now double click the mframe32 and mframe64 files individually. Do this step in different orders, you will get different results. You won't get both programs launched and their respective mframe files loaded without some kind of error happening.
i believe (although am not certain) that this problem stems from the fact that the four .app files call an underlying executable that is named the same thing called Vienna Ensemble Pro. The 32-bit and 64-bit versions of this executable are different but named the same. Both the VE Pro and VE Pro Server use the same executable. Both VE Pro (64-bit) and VE Pro Server (64-bit) use the same executable but different from the 32-bit executable. So if one of those two executables is already running and you double click an mframe file of the other type, nothing will happen or it will attempt to load VE Pro and get an invalid file error. I think this is because the OS already thinks that program is running and so will abort the launch. Or it is happening because the file associations don't work because of the executable naming problem.
I also don't understand why double clicking an mframe32 or mframe64 file will ever open VE Pro (the non server app). This always results in an invalid file type error.
Opening mframe files using the file menu from within the respective Server app always works correctly (although it is possible to load mframe32 files into VE Pro Server (64-bit)). I don't know if this is intentional or not. At any rate, opening files by double clicking an mframe32 or mframe64 file from the desktop should operate exactly like opening files from the file menu. Currently it does not.
I hope this description is clear and you can verify the problem as it exists.