I noticed that after some combination of keys pressed, the accents does not print anymore. After many tries I'm not able to tell what is the combination that cause this problem.
The effect is that è becomes e, à becomes a , etc...
Restarting rdesktop is the only way to fix this.
My specs :
Local System : Xubuntu 9.04
Remote System : windows 2003 server
Keyboard Layout : IT
Rdesktop : 1.6.0