[USB Audio] issues with Fiber KVM

Hello everybody.

We have to install some 3 years old Optiplex 790 in a control room, using Matrox Extio FD1220 fiber KVM: everything seems to work fine (video, HID devices), but we are facing some problems with the USB audio headphones and speaker that we are compelled to use.

In fact, the audio is always disturbed and almost unlistenable, even after upgrading every Optiplex Driver, having applied all the most recent Windows 7 X64 patches and having also installed of course all the most recent Extio updates.

The same OS and KVM configuration works perfectly on the previous Optiplex 780 model, using a PCIe fiber controller.

Has anybody had any similar issue?

Do you know if it is available any particular update (from DELL or more probably Intel) for this kind of problem?

Thanks in advance for your answer

Fabio