It seem at first to me that your processor may be on knee
having pain to process the sound but it could be something else.
1600x1200 seem a bit high to me for a 850 (I'm running 1184 on a p4 1.7 ghz ti4200 128mo)
Orbiter seem to "eat" process time, it run well but doesn't let many place for other process.
please try those and feedback how it goes:
-try to lower the resolution and see if the click disappear or lessen
-try to reinstall directx
-try to lower the hardware acceleration of your sound card
-feedback how many FPS you have when the click occure.
I don't know the phillips card and how it handle directx
but I know I had big trouble with kxdriver "zero latency"
especially done for midi music (vst cubase) I had to deinstall
them so I cannot do music and programing orbiter in same time

So this could have something to do with the buffer size, latency etc etc
of your souncard. Do you have some setting that you can alter
as latency ?
Dan