i always get the same prob as yours..
delayed write failed..

it happen when u try to copy a lot of file simultaneously..
what i'm done b4 is try copy 1 by 1..
it do take time...

it happen only when u try to copy file to it..
it didnt happen when u open that file..
it is what happen to me..

that is what im done b4, as for now......... i already throw that hdisk away..

so i didnt get that prob anymore...

my sugestion = do get a powerfull casing for ur xternal.. dont use the cheap one...