Thanks AntMAn,
Opening the project in safe mode was the first thing I tried to no avail. Does the same thing.
The audio does play in other players such as Windows media player so the tracks are ok.
I copied the project folder to another location but that doesn't do anything. Obviously I can't do a save as or anything like that.
It's definitely not the hard drive.
All my other projects open and play fine. I just don't want to do any recording in them in fear of this happening.
Before doing any recording I make a copy of the project just in case the project becomes corrupted but if it does all my work is for nothing. I could copy the audio tracks in a new project but they don't line up and will be a pain to line everything up. There is no obvious reason for this to happen. Maybe it's the update and I should roll back and see what happens. I will give that a shot tonight.
appreciate all the suggestions that you can think of.
Thanks