I'd hate to sound overly confident, but if you're receiving this error:
 
Unable to read/write data
Choose Help - Fantom VS Editor Manual, and refer to 7. If the
display indicates 'Unable to read/write data'.
 
Then I'd double, triple, quadruple check everything suggested in the article. I've helped hundreds of customers directly as well as tons of other vendors with troubleshooting that error, and I've yet to see a single case where that error was triggered other then the suggested reasons. You would be the first :)
 
The suggestions get pretty specific so I'm not sure what to suggest other then checking again. If you want to provide some screenshots of your settings that might help us all collectively.
 
(BTW, the Fantom VS is a 32-bit plug-in only. There is no 64-bit version of the plug-in. This really has no effect on the performance of the hardware since all of the processing is done on the hardware anyway. All it means is that it is pulled in via the BitBridge wrapper, but this is normal.)
 
 

I would love to post screen shots but I don't know how to do that.  In PowerPoint, I would do control-alt-print screen and then paste the screen shot into a PowerPoint slide.  That doesn't work on this forum.

Regarding the ARX, I am sure I did not do that.  When doing the Editor Install, I unchecked the bottom two boxes because they had to do with the ARX and a second Fantom.

to post a screen shot type snip in the search bar in windows 7
click NEW on the snip tool and drag the rectangle around your screenshot.
 
 
windows 7 comes with a built in screenshot software(I noticed in your sig your using windows 7)
 try uploading your photo to a cloud storage(free photo storage)
good luck sir.

I was alerted that John ended up calling in and our guys were able to help get to the bottom of things. From what I heard the error message was MIDI ports being routed to the DX-7 port, but there were in fact missing registry keys which is probably what caused a ton of confusion in the first place.
 
I'm not sure how comfortable everyone is with the registry, so if you ever run into this problem please feel free to call us and we'll walk you through the process. For everyone's records though, since I know this comes up more often then it should, these are the keys that need to be installed:
 
For 32-bit SONAR:
 
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST\HardwareSupport]
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST\HardwareSupport\ARX]
"Port 1"="ARX (VS-700)"
"Port 2"="VS-700 ARX"
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST\HardwareSupport\ARX (2)]
"Port 1"="ARX (2-VS-700)"
"Port 2"="VS-700 (2) ARX"
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST\HardwareSupport\Fantom VS]
"Port 1"="FANTOM VS (VS-700)"
"Port 2"="VS-700 FANTOM VS"
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST\HardwareSupport\Fantom VS (2)]
"Port 1"="FANTOM VS (2-VS-700)"
"Port 2"="VS-700 (2) FANTOM VS"
 
For 64-bit SONAR:
 
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST X64\HardwareSupport]
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST X64\HardwareSupport\ARX]
"Port 1"="ARX (VS-700)"
"Port 2"="VS-700 ARX"
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST X64\HardwareSupport\ARX (2)]
"Port 1"="ARX (2-VS-700)"
"Port 2"="VS-700 (2) ARX"
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST X64\HardwareSupport\Fantom VS]
"Port 1"="FANTOM VS (VS-700)"
"Port 2"="VS-700 FANTOM VS"
[HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST X64\HardwareSupport\Fantom VS (2)]
"Port 1"="FANTOM VS (2-VS-700)"
"Port 2"="VS-700 (2) FANTOM VS"
 
 
Basically easiest way to install these is to open up Notepad and at the top type the following:
 
"Windows Registry Editor Version 5.00"
 
Followed by the keys listed above. Afterwards, save the file as a .reg file. If you click it afterwards Windows should prompt you if you want to import the keys into the registry editor, and warn you that this is probably not a good idea. For this reason, if you want help we definitely don't mind giving a hand. It's a sensitive area to mess around with things. Unfortunately I've been at the other end of a call before where someone deleted a huge chunk of keys and couldn't boot into their OS. It's not fun to deal with.
 
Hope that helps for you guys if you run into it.

Thanks, Ryan.
 
Dean was extremely helpful and patient while spending quite a bit of time with me on the phone.   I so greatly appreciate getting things up and running with the Fantom soft synth.  
 
John

Oh yes, I decided to call because the registry (to me) was intimidating.
 

Thank you for YOUR patience. I know it's an incredibly frustrating issue to troubleshoot. Honestly, from the user end, I can't imagine anyone would ever know to look for those missing keys. It's a really weird situation to get into. I've yet to figure out how to replicate getting to a situation where the keys don't install, but I obviously know it happens because users report it.
 
Anyhow, I hope you enjoy!! There are a lot of classic sounds that I hope will help you to get lost in writing some music versus troubleshooting computers :)

Yep, had the same exact issue with my setup about a year ago.  There was actually a registry file tech support had me download and run.  Bam, fixed.  It probably still exists out there somewhere.  Nobody knew what caused the issue, but it was--and is, apparently--an uncommon (and uncommonly frustrating) glitch.  Glad you got it all sorted out!  :)

The reg hack just fixed my problem.
Thanks for posting.