some speakers have a Left&Right switch, i.e. beolab 4, if you have both set to right, that would explain the problem

The left speaker was in left position and the right speaker in right position - with no sound coming from the left speaker.

I then tried putting the left speaker in right position, and now i have sound in both speakers (right channel only). so i know it is the left signal that is missing..

I think i pressed something like menu + navigation-button and the something? Not sure though..

I have tried resetting everything again.. It is actually only through AUX the audio problem is current, when playing music through airplay there is no problem.

However the left signal has a bit of 'noise' - a very low sort of 'beeping' sound?

I'm just talking to myself now, but perhaps someone will encounter the same problem in the future, and will read this :-)

I spend most of my evening trying to fix it with settings on the beo4 / playmaker. Ended up fetching new AUX-cables at my place, and hooking it up with these, and now both channels play :-D  I have absolutely NO idea how the two things are connected, but they must be?

I do still feel that, when the volume is turned all the way down, and ONLY when playing via airplay there is a bit of humming from the left channel? Any ideas why this is?

Mace

So your cable was defective.

what speakers do you have? There is a slim chance you got MK2 powerlink cables whilemyou need MK3. That can cause humming but since your setup is recent this is most likely not the issue

Might be worth to drag the entire setup to your dealer and try there ....

it's my parents setup, and it consists of a playmaker connected to 2009 Beolab 6000 speakers. It's RJ45 -> power link,  And i think it's MKII-cables.

I thought MKII could be used to all B&O-speakers?