My Edited Films Have Funny Stuff Round The Cast

The first thing that comes to mind is the quality of original footage.
Remember the old saying 'garbage in, garbage out' if the original source is below par there is no magic that will ressurect it.
Check that a a starting point, secondly your mail is a bit vague on what kind of editing you are performing to the footage. If the quality is good coming in then you are definately doing something in the editing process which is destructive.
These are the two possible causes of poor output, opps thirdly, afte compositing there is also the possiblity of output quality errors which may also occur when the footage is being digitised depending on what particular process or workflow you use.

Hope this helped some.