SigmaStudio with EVAL-ADAU1781Z, USBi problem

Using SigmaStudio with the EVAL-ADAU1781Z and the EVAL-ADUSB2Z, we have successfully followed the quick start guide and after a download, microphone input can be heard at the speaker outputs.

But only a single USBi transfer will work, subsequent downloads or on-the-fly changes fail, with the status "Compiled Comms Failed". A USB reset (physical disconnect or Device Power On/Off from the menu) is required to get the USB going again - for a single operation only.

At the capture window, for the first USB transfer, there are multiple Block Writes, a Read Request and finally a Read Result. For further USB transfers, there are multiple Block Writes, a Read Request, but no Read Result. It seems that the USB is getting locked-up.

SigmaStudio is running on Windows XP.

This is the first time of using SigmaStudio and the EVAL kit. Is there something else that needs to be done with the USB?

Thanks in advance,

Mark.