I don't have much to say, but a wireless network connection that's able to do something non-real time, like download a s/w update, may not be fast or dropout free enough to handle real time streaming of audio content. For downloading s/w bits if a data packet is missed it can be rebroadcast, typical TCP/IP kind of thing.

But, you've got some serious money there, and your issues are indeed troubling. Hope you resolve them soon, or run a wire rather than wireless and see how that works. I was all hot to pick up a 2nd life pair of BL5s to replace my 9s, but having read your issue with them and others here, I think I'll stick to my reliable 9s.

Good luck with the issue.

None of the music I play is streamed – all content, both video and audio, is wired. I will indeed try the speakers with a wired internet connection, and ask my dealer to check all connections for earthing, to see whether that solves the problem – if not, I will have to request a replacement pair. I have read about other people experiencing software problems with Lab 50s, whereas I have never heard of a pair of rogue Lab 90s.

Have you scan your area for wireless signal traffic?

Not sure how to do that.

I tested the BL50s again last night – they just produced the humming/buzzing when connected to the BeoSystem 3 but immediately performed normally with music through the line input.

That suggests a simple cable failure, but my dealer and I are baffled that the slave still performs normally with the BS3 – wouldn't a cable failure affect both the master and slave?

That could be Beosystem3 bug,.Recently,I had humming/buzzing on my right surround beolab 4000 mk1 powerlinked into Bsys3.

Unplugged both power from mains,and powerlink from Bsys3 overnight.Next morning all OK.It is worth a try.

Anyhow,you have expensive boxes under warranty,worth service attendance.