Remote Desktop via VPN - black screen

Archived from groups: microsoft.public.windowsxp.work_remotely (More info?)

Since a couple of weeks I have a problem with remoteDesktop via VPN. A
while ago it just worked, but now it isn't anymore.

The situation:
pc with broadband at home
servers & desktops with working Remote Desktop at work (with working I mean,
it works IN the network and I have set up a couple of users/passwords to
login)
VNC viewer works (for the pc's where it is installed on - otherwise you can
say, just use THAT)
pinging to the host computer also works
XP sp2 installed (hosts & guests)
at home : no domain
at work : domain

When I try to start up Remote desktop, and I click connect after filling in
the IP address (I already found out it does not work with pc names), I get a
black screen (in full screen mode) and the computer is blocked. Then I get
a message : "the connection to the remote computer was broken. this may have
been caused by a network error. Please try connecting to the remote
computer again".

Now I think it has something to do with portforwarding, but I shouldn't know
how to configure IF it is a portforwardingquestion. My router is a Topcom
WBR 244

Thanks in advance !

Note: I also found a similar (the same) question on
http://www.eggheadcafe.com/ng/microsoft.public.windowsx...
but there was no answer....