Annoying bug with digital source on Onkyo AVR

[El_Roberto]

I recently bought a new sound card to use in my main computer, the Asus Xonar HDAV1.3. I have it connected using a coaxial cable and it causes my Onkyo AVR to keep changing between differnen't encoding's, when this happens the speakers make an extremely annoying tapping sound - the front of the AVR can be seen to be skipping from the preset mode (Dolby DTS, I think) and "Dialog Norm +4", however when I try and set the preset mode to "Dialog Norm +4" it is not an available option! It only seems to do the skipping when I change webpages on internet explorer, or if the computer is reset it will do it when I first open any program that uses audio (WMP, VLC etc.). Any idea's on how to fix this?

Specs in sig + the HDAV1.3, HT setup is an Onkyo TX-SR601 with Yamaha YST-SW315 sub and 5 channel B &W speakers, as stated using COAX input, this doesn't happen with analog in.