Hello Sasha,
I suppose the OCX is compiled for 32-bit, so thats probaly the cause why it is not working in 64-bit.
You could start a dialog in the 32-bit version with the function "ExtProgram" when you start DIAdem 32-bit with a parameter as a startscript. The startscript would run the dialog and when finsihed close the DIAdem 32-bit instance. You probably have to load and save some kind of data in the 32-bit version to exchange information with the 64-bit instance.
Command: ExtProgram - DIAdem 2011 Help - National Instruments
http://zone.ni.com/reference/en-XX/help/370859J-01/comoff/extprogram/
That anyone could help you with alternative controls, it would be good to know, what do you need those controls for?
Is there a 64-bit version for that library. Since that question (Any appropriate 64-bit Controls?) rather seems a Microsoft/non-DIAdem one, perhaps you should seek help for that part in a forum specialized with that.
Of course I try to help you along in all DIAdem related stuff.
Best regards,
Christoph