Windows 7 Home Premium SP1; Audacity 2.05; .exe installer
Been using Audacity for a while with no problem.
Today, tried to open an mp3 file, and nothing. Just a flat-line for the duration of the music
Tried generating some White Noise; again nothing just a flat line for 30 seconds
It’s almost as if I have MUTE set, but I don’t. The Gain is set to 0.0
The same mp3 file plays fine in Windows media player
What setting did I change?
When was the last time you restarted Windows?
Koz
Just tried restarting windows - It did not fix the problem
I still just get a flat-line
Neither Gain nor MUTE affect the blue waves. I assume you don’t get the green sound meters, either?
Koz
You mean that the waveform display is visually a flat line (and silent on playback)?
Are you logged in to your computer with the same user account that you were using previously?
Look in “Edit > Preferences > Directories”. What does that show?
C:UsersVinceAppDataLocalTempaudacity_temp (Vince is my login name)
I deleted that directory, restarted Audacity
Audacity re-created the directory, and all is well!!! 
Many thanks!