I just discovered this nice tool to analyze the disk space usage in local or more important, in remote pc.
Baobab is a graphical, menu-driven application to analyse disk usage in any Gnome environment.
This is how my Downloads folder looks like using Baobab
Baobab uses ssh to obtain the data it needs and you can launch it with :
ssh user@url -Y baobab
So you can check easily when some of the remote machines you are working with, is complaining about disk space!