thanks a lot for the reply, but I need to clarify something:
You think the slow application loading is caused by the network?
I think it's something else. I've noticed that it happens only to
KDE applications (kedit, kwrite, konqueror filebrowser, and when
trying to open the 'file open' dialog which have the kde default
dialog, sometimes when I press on the kde's 'start' menu).
To other X apps it does not happen, and also it does not
happen to every kde app.

About the network card, I'll try your (2) suggestion. thanks.