In case anyone is interested, I downloaded the latest 6.4.3 and the transfer rate to the USB drive is much faster. It depends on the blocksize. With 512 bytes it was 1.1MB/s and with 32kbytes it was 21MB/s so that's going to be great for the job I want to do.

However, usbview still shows that the USB HDD is only 'full speed' and not 'high speed', and the Windows usbview utility says the same, so they do not seem to be able to detect that the HDD is able to use the 'high speed' mode.

Peter