Rear sprocket movement.

Originally Posted by muzikill

Id say if the there was a spacer worn or missing and the sprocket hub/carrier was loose then the wheel would have play in it. If not then the sprocket mounting nuts must be loose?

Absolutely, the OP might not notice that with the bike on the ground though.

Poss the wheel bearings gone? Have you recently had the rear wheel in or out?

[Bibio]

if the whole wheel moves then i would suspect that the inner spacer is missing and if so then its knackered the carrier bearing.

axle nut loose.

if just the sprocket carrier is moving then i would suspect the carrier bearing is shot.

very unlikely that 5 nuts have come loose unless some numpty has fitted a chain and sprocket kit then forgot to tighten the nuts.

[Sid Squid]

As Bibio says; most likely carrier bearing.