Will no longer save my files to disc or export them. Will only save within Garage Band?

I've been uploading podcasts to my website which in turn puts them on itunes but this week suddenly, garageband will no longer "export to disc" or when it does it will save at twice the file size it estimated. When I try exporting directly into iTunes the "song" never exports (though no warning appears saying it's failed) and when i export to disc (i.e. desktop) the file also doesn't show up on desktop. I can, however, still listen to it within Garage Band. Although that's useless pretty much since the files are meant to be shared.