i had the same issue with my unit when i first got it. and the support was pretty much the same. i've done all this USB replacements, cable changes, PC OS reinstallation, Virus TI OS reinstallation even before they were telling me about this.. and the problem gone only after unit replacement.. in my case i had to wait for the replacement for one more month because i ordered my virus from the states to israel to save some cash but in the end i even spended more then if i would buy the unit in my country.
happy that everything is good for your now and you can enjoy the virus sound.
PS. now i'm pretty afraid to install the new Virus TI OS5.