I have recorded approx 100 dvd's and experienced no problems (Princo A-grade) but all of a sudden I am getting error message U11....and damaged approx 17 dvds .....have used a cleaning lens disk which worked on some dvd's but not on others...the problems occurs approx 1-2 minutes after starting the recording...then the machine shuts downany help would be appreciated....also ....is there a way to check if the dvd is ok ...or if the dvd disk has already some problems before starting recording? thanks