From the DVDplusRW FAQ:
"On Philips and Yamaha recorders, you might try the following procedure ... (from firmware version ff11 onwards): Open the drawer of the recorder and insert the corrupted DVD+R disc. Do not close the drawer! Press and hold the '4' button on the remote control of the recorder. The drawer will now close, and the displays shows "Finalize". The recover-operation (sometimes being refered to as 'Forced Finalize') now starts. This will take about 3 minutes. The recorder looks for the last non-corrupted table of contents, and uses that info to finalize the disc. After that you cannot record on the disc anymore but at least you may recover most if not all of the recorded content."
Sometime the normal finalising can take a few minutes as well.
Do not use the "5" button unless you know what you're doing: this makes the recorder attempt to recover a lost recording, which can take up to four times as long as the length of the original.
Edit: All this is assuming that you are using +R, and not -R as stated.