Nero 7 Ultra Edition DVD burning Problem

Hello. I'm quite new here and I'm having a problem with Nero 7 Ultra Edition.
I recieved the Nero 7 software when I purchased the Sony DRX-830U DVD/CD rewritable drive months back. I've burned many DVD-Rs, both 4.7 & 8.5GB discs, and everything was fine until recently. When I attempt to burn the files to disc it gets about 3 quaters into the encoding process and then Nero just closes very abruptly with no error message or anything. Afterwards, when I try to play the disc (although nothing was burned onto it) a "need to format disc" message comes up; this is a first and I don't know why it asks me to do this. I'm at a loss and am leary to try another disc.
Any clue? Thanks.

You can find out why Nero is aborting by checking the Nero burn log. It's called "NeroHistory.log". It's usually in your Nero program folder, but search for its exact location, then click on it to read it in Notepad.