This is a Samsung DVD recorder - I've had the exact same problem - By the way, don't you mean "this disc cannot be recorded" ? These DVD recorders are known to reject certain type of discs.
* Have you updated your Samsung with the latest firmware ?
Follow the instructions carefuly and please understand the risks involved in flashing your drive - Do not interrupt the process, it can take long.
* here are the brands of DVD-R I have used successfuly with this recorder int he past:
Taiyo Yuiden DVD-R 4x / 8x (the optical drives used in those recorders are outdated, their writing strategies are never up to date and may not recognize some type of discs)
Maxell DVD-R 4x / 8x
Verbatim DVD-R 4x / 8x
Try another blank disc - maybe it will accept it - if it keeps rejecting all your blank DVD-R no matter what brand, you have a bad drive inside your recorder - the samsung recorders are **** - I have ever since gotten rid of that piece of **** and now use a Sony HDR-780 HDD/DVD recorder, uses pioneer components and is great !
Avoid those lens cleaners - they can do more harm than good!
I hope this helps.
Try different brands of DVD-R, avoid the cheap generic **** - drives like best Taiyo Yuden & Verbatim media id codes - they should recognize Maxells, verbatims, sony, taiyo yuden, ritek. if it keeps spitting out all discs you use, you have a defective unit. The latest firmware on that drive should also help !
Good luck :)