Hey Frank, I had the same problem very recently. Might be worth checking the thread.
http://forums.creativecow.net/readpost/2/927308
Basically it turned out that I was rendering JPG sequences with unmanaged colour spaces, meaning that each rendering station was imposing it's own colour profile into each file it was rendering. Hence the flicker you are probably witnessing when you pull the sequences back in.
The solution is to make sure that the initiating machine has set a colour space for the project. I quote Darby "The working space is defined in the Project Settings of the project."
