This seems to happen only on Windows, and only in particular situations. We don't understand exactly when.
(Should we add more info here on which Windows versions, etc.? Does that matter if somebody has hit the error)
The problem seems to involve the USB connection to layout hardware.
It has been found that this issue is seen when using certain Digitrax PR3 interfaces in conjunction with 64-bit versions of Microsoft Windows.
This appears to be related to a firmware issue on earlier models of the PR3 interface. Digitrax have issued an updated version of the firmware that can be installed onto the PR3 interface.
The firmware can be downloaded from the Digitrax website.