A "Data Too Short" message indicates that the track and virtual track that is being selected for burning to a CD does not have any audio recorded on it. Be sure to bounce the tracks prior to burning a CD and then select this bounced track and it's virtual track when burning a CD.
Use the following article to guide through the Bounce process (which also explains how to check which V-Track is being used) and CD burn process: BR-1200CD: Burning Your Song to a CD