I have just purchased a Sony BDV-590 one box solution. It would be great, but I hear a continual (very) high frequency sound coming from it. It is particularly bad when HDMI 1 is selected. No-one else can hear it until I point it out to them. Has anyone else experienced anything like this? I would love to exchange it for a replacement, but fear that it won't even be noticed by the supplier when checked. Is a certain amount of background noise acceptable? Any guidance would be appreciated.