The DFC90 "Audio Fail" message requires the Avidyne Dealer to RMA the unit. 

Please use the 'Find a Dealer' link at the top of Avidyne.com to find your closest Avidyne Dealer. 

The card has become "corrupted" due to the fact that it writes information and deletes old information. 

This can only be done a certain number of times before the card becomes unusable ("corrupted") and requires replacement.