booting problem-please help!thanx

[martiemcd]

i have just had a ps2 chipped for my nephews birthday{tomorrow} and saved a few quid into the bargain,as i already had a spare copy of dvd region x.
but it wont boot! i checked some backups with it last night in my ps2 and it as usual booted ok,but it wont boot at all on my nephews...........................???????????????? ?????????????????????????????????could it be anything to do with one machine being a version 5 and the other not? or just a slight laser difference between the two machines.........everything else boots fine,backups,ar2,ps1 etc....just the damn region x..........any advice anyone?.............thanx...........martiemcd.