[margi]

I have the similar problem - a/v drift after small errors in stream. May be only after some time streaming... Source is linux server with cards and tvheadend or windows server with dvblink or mediaportal. Result is same - drifting. I tried rpi with all major xbmc releases and always the same.
On the other hand, i can use apple tv 2 and this is always without problems....ok, i have no HD