VNC enterprise eats a lot of bandwith.

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I am using VNC enterprise edition 4.1.7. on WindowsXP Pro (both pcs)
Everything worked fine untill last week. When I run an application on the 
remote pc that uploads continuously (like a video encoder, an ftp program or 
a torrent program) and I connect remotely the bandwith becomes very unstable 
(from 0 to the maximum upload speed) disturbing the programs that use the 
upload speed that very moment. Disconnecting VNC from the remote pc will not 
return the bandwith to regural status. I am sure VNC is the problem because 
if I leave the remote pc alone without accessing it everythings works fine 
untill that very moment that I will connect.
Can someone help?
Spiro Karabalis