Thanks very much for the swift reply and the link to the updated BIOS. I have applied it and will report back after a few days of running it.
Thanks again
Well, after 48hours of running with the FB11 BIOS I am pleased to report that I have not had a single crackling sound
I've still got DPC Latency running and I have spotted the odd spike, but it's a one-off every now and then. By one-off I mean a single instance of latency, rather than a 10min chunk.
So as far as I'm concerned, whatever changes are in FB11 to resolve this issue need to make it to the proper release.
For info, I have also re-enabled the Windows Indexing Service and all seems to be fine with that too.
Thanks for your help