When you're writing a DVD Studio Pro 4 project to a DLT (Digital Linear Tape) drive, the write may stop and you'll see the following error:
"Format Failed. Not enough space on output device."
You may get this error even if the layer size of your DVD project is smaller than the DLT tape to which you're writing.
To resolve this issue, update to DVD Studio Pro 4.0.3 by using Software Update, or download the updater from here:
http://www.apple.com/finalcutstudio/dvdstudiopro/download/