I'm on Sonar 8.5.3 x32 and Windows 7 x64 and got faderport to work just fine, but had a little bit of a hassle at first.
When you download the presonus faderport latest drivers, you have a folder for sonar, that contains .dll files for both 32 and 64 bit.
You need the 64bit files.
You have to copy that .dll file into cakewalk shared surfaces.
Then you might have to register it:
Click the Start button on windows taskbar.
Type RUN in the Search line.
Open RUN.
Paste this, replacing with your own .dll file path:
regsvr32 "D:\Sonar\Shared Components\Shared Surfaces\faderport.dll"
I hope this works. It worked for the 32 bit version. BTW you might have to put regsvr64 for the 64 bit version (i'm not sure).
Try it with regsvr32 first and see if it helps.
Cheers!