Dell Studio XPS 8100 / BBC iPlayer Constantly Rebuffering

Hi folks. I was advised to re-post this from another Dell forum...

In what is becoming an endless stream of issues with my new Dell XPS8100, I wonder if anyone can shed any light on this:

I use the BBC iPlayer a lot - every day for four or five hours in fact -  for listening to radio shows.  Since getting this new Dell it is continuously rebuffering every three or four minutes and I even occasionally get a "There is not enough bandwith to play this programme" message after a few minutes.  It's impossible to listen to anything anymore.  This does not happen with the TV streams (I think!), even the HD ones; only audio.

I have an account with the Geek Squad and they tell me that, although my broadband speed is 7mbps, this new machine may require a faster connection.  There was a wiff of a suggestion that some of the RAM hardware might be knackered but he thought this to be unlikely.  My broadband provider (O2) says there is nothing wrong.  I have also tried alternative browsers such as Google Chrome but get the same problem.  I've run every broadband speed test you can think of, including the iPlayer one, and am maintaining a good 7mbps speed.

I'm on Windows 7 Ult 64-bit with 8gb RAM and am connected to the router by LAN.  This was not an issue with my prevous Windows XP computer so I can't see how it's anything to do with my broadband connection.

Has ANYONE got the faintest clue of what might be happening?