Problem BD Drive - any ideas

[pewe]

I have a BD drive in my Acer Laptop (BC-5500S). (Dual boot Win7 and Vista)

It was reading BD ok until the other day.

Now it will not recognise new BD discs - I say new because discs it has read before will still read occasionally (maybe once out of 10 attempts).

Can anyone suggest any reasons why the problem has suddenly appeared.

Acer say it is a software problem, but if I re-boot the PC into Vista instead of Win7 I get the same problem which I never had before, and it still reads CD and DVD - although I'm not familiar with the differences between these and BD - in both OS.