This happened to me a month back. Minute freeze up in the recording causing a gap.
What didn't work:
-Transferring the file
-opening with CD wave straight off the iRiver
-opening with Audacity straight off the iRiver
And what did:
-opening with Soundforge straight off the iRiver
Just experiment till you find something that works.
The gap then needs to be closed up in your editor, and resaved.
I'm considering junking the HD this happened to, and CF-ing the iRiver.