When testing the USB Pre, we several times got no response from the USB Pre. In order to make it work again, we pulled out the USB cable from the device and pulled it in again. That worked fine, except that once we had to go to Measurement->Sound Card... and reselect the input and output device to USBPre.
If you download the latest beta verison of WinMLS this should be solved.
Gaps during the measurements. We had problems when performing measurements using several averages. This can be solved by following the procedure given above, selecting the input channel 2 for deconvolution.
See the troubleshooting section of the USB Pre help for more information.