Sustain issues

Yeah
all my strings on my bass sutain just fine... apart from my d string.
whichever note i fret, my d string sustains maybe half as long as all the ohters
does anyone know why this could be?
Im thinking maybe a crap nut or bridge but im not sure

It could be the string Have you tried different strings? Sometimes you get dead strings out of the box apparently (which I expect will be replaced with an angry phonecall )

Theres a number of possibilities.

1 - Dead string
2 - String not sitting in nut slot properly, check for dirt in the nut slot.
3 - Bridge saddle issues, dirt, bent screw, string not sitting in saddle slot.
4 - If the saddle has 2 screws to adjust the hieight then make sure that both screw are making contact with the bridge.
5 - Twisted string
6 - The break angle - the angle at which the string leaves the nut and goes to the wraps on the tuning peg. the greater the angle, the more sustain and make sure the string is wrapped 3 times around the tuner (I wont go into the correct way to string your guitar as i assume you already know this)
7 - If its a fender type bass then this is known as a design flaw

Argh now I'm going to have to check how long all my strings sustain for, you've gotten me all paranoid

edit: Ah, my strings all sustain nicely. I think the D and G strings sustain longer than E and A but maybe that's just because they're higher notes?

yeah i think it might be the not enough wraps around the tuning peg
i didnt think it mattered how much you got around there so its only like 3/4 wrap around it
thx for the heads up