A sound problem - playback is at half speed

Hi,I have swapped to another machine and reinstalled FS9 and PMDG737-6/7/8/900. Everything sounds fine until I move back into the 2D cockpit after viewing from the outside, from that point on all of the sound effects including ATC and the co-pilot aural alerts (i.e. 80 knots etc) are now playing at only half of their normal speed. Before switching to the outside view the sound was normal and ATC speech was at normal speed. As soon as I reenter the 2D (using "S") the sound drops in frequency and ATC from then on is like a record (remember them!) at half speed.Has anyone else experienced this?