Transfer Problems

[Linux]

Rsync has been a roller coaster ride for me..
One day it works fine the next day it doesn't.

The error i'm recieving is :

rsync: connection unexpectedly closed (399 bytes read so far)
rsync error: error in rsync protocol data stream (code 12) at io.c(165)


What does this mean and or hint to as the problem?

Also is there a Limit on the size of files Rsync can successfully
handle?

Thanks
Edward