USB redirection for Thin Clients (accessing local USB devices form remote session) was a big problem for us with HP thin client. We deployed USB over IP SW solution from Eltima eltima.com/products/usb-over-ethernet/ everything works fine now with HP.
But I've recently found that Oracle have added remote USB access support and here is the instruction:
wikis.sun.com/display/SRWC2dot2/Managing+USB+Device+Redirection+%28All+Topics%29
Hope this helps