Why has my dvd burner suddenly gone back to 2x burn from 4x

i have a optirite DD0201 model, and last year, when bought imediatly updated firmware which at the time made my burner start burning as it should at 4x speed doing a dvd in aproxx 15 mins as they do.

now for some god knows reason why its gone back to doing the dvds at 2x taking half hour a disk, now few pointers so u all know…

using exact same media as always,

checked dma (and changed back to pio then back again, with restart each time)

ive tried all my usual software (decryptor, nero, shrink)

just for some reason its doing this and its driving me mad, plzz anybody any ideas why.

any help much apricated.