I am just trying to get a better picture in my head of your configuration, so please bear with me.
1. Is Sonar installed in 64-bit mode?
2. Is BFD2 installed in 64-bit mode?
3. Here is a link from the web site for BFD2:
http://www.fxpansion.com/index.php?page=53 Perhaps that is something you could look at doing, if you haven't already.
IF you are attempting to run an older version of BFD2 as a 32-bit module, within a 64-bit Sonar, you then need to use a piece of bridging software to allow it to run. Sonar comes with such a bridging application, and it is called BitBridge. Please note that it does not fix ALL situations for all 32-bit modules to enable them to run in 64-bit Sonar. It MAY work, or it MAY not.
For the cases where BitBridge does not allow a particular 32-bit plugin to run properly in 64-bit Sonar, there is another piece of bridging software, called J-Bridge, and it may or may not work either, but some folks have reported it working for certain 32-bit plugins, so this is another potential way to go.
In the link I posted above, the makers oif BFD2 DID release a 64-bit compatible version of BFD2, so I would start there.
Please note, that some of the discussion I reviewed ALSO indicated a reliance on particular levels of C and C++ routines needing to be in place for the software to run properly, so I encourage you to apply ALL recommended updates for your version of Windows, until it finally tells you there are no more updates to apply. This way, you head that error condition off at the pass.
Good luck,
Bob Bone