Network slow when XBMC running

Hi,

I have a strange issue., I download tv on one PC and then transfer them to the server/streamer. These are both on a wired 1 GB network.The strange thing is when xbmc is active on the streamer (playing or idle) transfer speeds are slow. If I close down xbmc then the transfer immediately speeds up - I'm talking a few seconds to transfer a 1gb file rather than a minute or 2. If I launch xbmc while the transfer is in process then it immediately slows down

Any one got any ideas why XBMC would have this impact on a transfer?

Everso.