Hi Hubert,
You probably will not want to hear this but,
You cannot have a window open to the RT system while running a different LV app on the host.
When I have needed to do this, I have cabled up another PC with LV-RT to monitor the RT system. Een doing this can be a little awkward because RT wants to re-link and reload when you switch to the taget RT system.
I got around this by mapping the drive where the RT app is stored on the the windows system to the "extra" PC. Even after doing this, make sure you do clean connects and disconnects (to from the RT system), otherwise it seems that the main RT app will close but leave al of the sub-VI's running!
I have used other techniques as well, but they may be to specific to comment on now.
What kind of thing
are you trying to debug that requires you have both systems going at the same time?
Ben