Suddenly stopped reading discs (error msg: "unsupportable disc")

My Panasonic DMR EA14 (DVD recorder & player) suddenly stopped reading/playing certain discs that I recorded & finalized myself & have watched many times. The error message says, "unsupportable disc." Although I can still watch these disc's on my MacBook. The Panasonic DMR EA14 DVD recorder will still play store-bought, pre-recorded DVD's. I'm also having problems recording on discs that previously recorded just fine and still have plenty of recording time left. Hope someone can help. Thanks very much, Julie.