Problem solved, the router needed to be rebooted. Now it works..
I have installed xrdp on the linuxbox (mint 11 katya) and rdesktop on the Nokia N900 (debian squeeze) cellphone , and enabled port 3389 in the router.
It works perfectly on my private network (much better than vnc..) but when i try to connect over 3G then rdesktop quits with "connection reset by peer" or some similar text.
I am guessing that it is something securityrelated in xrdp when the connection goes thru the router, since i also have tried other ports than the default 3389 just incase that port was blocked by the 3G network.
So, what settings do i need to change for xrdp to accept connections over internet? (where is the settings for xrdp?)
-There is also something called "domain" below username and password in rdesktop, what is that for?