Roxio creates temporary hidden movie files during capture. I assume after a succesful capture, it deletes these or unhides them. However if a capture fails these files remain hidden in the Movies folder taking up a large amount of space. In order to see these files to delete them, you need to open up Terminal in OS X utilities and modify the user defaults file by entering this:
defaults write com.apple.Finder AppleShowAllFiles TRUE
*If you're running 10.9 you'll need to use a lowercase "f" in Finder.
and then restart Finder:
Navigate to your Movies folder and delete any hidden file that has the .mov file extension.
To revert back to hidden files enter:
defaults write com.apple.Finder AppleShowAllFiles FALSE