See my previous(solved) question here:

thanks to those who help me solve that problem, but now it's causing another.

The crates/actors in the maps have collision, and when you touch them or walk on them or whatever, your movement is very jerky and u sometimes seem to get thrown off.
I think that the client thinks you can walk through them, and the server is putting you back to where you should be.

any help would be much appreciated.