Was beaten to it!
Something else to bear in mind (and a few other threads or people giving anodectical evidence of this)
is that further to bad brand of cd/dvd, bad burn, fussy players, there is also the case
of good burn, good player but cd/dvd ever so slighlty warped or not well balanced,
so even 2 dvd from a same pack can have different behaviour
(I have burnt mandy 2007.1. on 2 dvds one boots, the other does not, thanks to the fussy dvd-player
of an IBM laptop)
and here goes those errors that make little sense
Sometimes dvd players need cleaning as well