I would say the item recorded on a 'bad' part of the disc that + records to. If so, you won't be able to play it.
Sometimes when its happened to me, I power it off for a few minutes at the switch, then turn it back on and *sometimes* it works.
We have cornation st, emerdale etc on series record (sad or what!) a month or so corrie taped but would not play so just deleted and forgot about it, same thing happened on fri nite it taped the first episode and taped the second episode but would only play the second episode - should we ring sky or could we sort it out ourselves