Song Save fails to copy files over in some cases

Twice now I have had an issue with File -> Save Project As failing to copy over the files and the project folder ends up empty.(for the samples only) The pattern data seems to be in place but the audio is missing. I noticed that last night the save operation got about 75% complete according to the progress bar, and just hung there. The other time was a day or so ago and it looked like the save completed normally. Not dismissing the possibility of a bad sd card here, but has anyone else experienced this?