rdr hxd 970 will not accept dvd-r discs

[rallychief]

Hi everybody just bought 25 maxell dvd -r discs and the 970 won't record to them it loads them but when you try to dub to them it brings up message wrong type of disc please load a dvd+r  am i doing something wrong the machine should accept a -r no problem according to the manual

[rallychief]

just to add to the problem seems putting the -r disc in it has screwed it up, now won't record to +r discs either it will allow you to name disc then go to hdd-dvd dubbing screen then select the item from title list to dub then will go to the screen which says next, then will go no further.