BMX Sprocket Different Than MTB?

[Hawk 5420]

ok i have an 06 gt ruckus UF and i messed up the back wheel. so for X-mas i got a set of mavic deemax rims. i wanted to put a 9 speed cassette on the deemax and just use it on the ruckus as a single speed. the reason for that is so when i go DH i can swap the rims over to my bighit and not have to be pulling the cassette all the time. my problem is when i got everything set up the chain i bought wasnt lining up on the front sprocket but it fit fine on the cassette. do i have a BMX front sprocket or something? and if so can i just switch it with a MTB sprocket or do i have to change the crank too?
thanks alot
shane

[Wumpus]

You might have a wider chainring if there is only a single ring. You'll need to pick up a 9sp chainring then.

[w00dy]

A narrower chain too.

[Gopher]

you can use a bmx sprocket with a 9spd chain as long as its the 3/32 tooth size otherwise no dice profile makes them in about every color and size you could ever want in the 3/32 size.