Help please! I've just invested in my first AV system. Got a Denon AVR 1804 receiver and KEF 2005.2 speakers. Films (in Dolby Digital) and music (in 5 channel stereo) sound great. BUT I'm a bit confused by Dolby Pro Logic 2 - when I choose this option and watch TV programs through Sky Digital I'm getting a strange high pitched "chirruping" sound (best way I can describe it) accompanying dialog from the front left & right and the rear left and right speakers - centre is fine. Can anyone explain this? If I select 5 channel stereo the noise disappears. Am I doing something wrong or does PL2 only work on cetain programs? P.S. - terrestrial reception is very poor in our area (we're in a valley) so I watch virtually everything thru Sky.