hi MB the things that spring to mind are
did he select "no multisession" in the multisession tab menu. If not the disc will be left open ie not finalised.
Also he should select "finalise disc"
Finally a dvd disc should be burned as dvd video. If it was burned as dvd rom it won't work.
Personally i never use +R, i find -R to be more compatible with a range of dvd players.