I came back to this issue and am having the same problem. I downloaded the framework Phidget-x64_184.108.40.20611121 for the Windows 7 64bit Professional Machine. The programs I am running are all from the samples and include the sample InterfaceKit-full.exe. I also downloaded the VC InterfaceKit-simple sample, compiled it for both x64 and x32 and all have this problem.
All is OK if I run the application quickly after inserting the USB cable. If I wait, the device is not seen. I am not running a Logitech Mouse.
If you send me some contact information, I can get you attached to a development machine which is showing this problem and you will see the problem in about 3 mins.