I don't have JRiver, but for Foobar's hiccup turning Wifi off helped and hiccup was gone. MediaMonkey was fine with no hiccup even with WiFi on. So it probably is software/hardware related problem. Did you try to close as many running apps as possible so that JRiver was only app running? What about Foobar?
Edited by PiNa.cz - 1/22/13 at 4:23am