Playback Issues with USB speakers

I've identified a playback problem in Nightly build R4859.

It seems to be specific to my Trust USB speakers as trying after a reset on my normal laptop sound system worked fine, but plugging in my USB Speakers again repeated the following behaviour.

For some reason the playback data is not getting through to the USB device properly.

On the piano voice after inputting a scale of 6 notes, only the last two sounded on playback.

On other voices you can hear the full scale, but the Note Offs are not being recognised by the USB Audio system, consequently there is a bad case of MIDI Echo!

Typically info on the hardware is sketchy - it describes it as "Generic USB Audio" in the Manufacturer field.

I can give a list of the drivers if you think it would help.

Also changing the instrument sound in the Mixer is not working neither in my normal laptop sound system nor the USB speakers