chain jumping when in gear...

[darrsi]

I have been doing a bit of Googling on behalf of an issue with my bike and stumbled on an article where someone was complaining about a 'clonking' noise and it turned out to be very worn cush drive rubbers and the sprocket holder had no tension on it at all, so i s'pose that could be mistaken for movement in the rear wheel?
Apparently it can also be responsible for jerky running at low revs as well.