blackbox X server error

[Rick]

I'm receiving the following error message each time I try and start blackbox:

 BaseDisplay::BaseDisplay: connection to X server failed.

When I try to run it from X I get this messsage:

BScreen::BScreen: an error occured while querying the X server.
  another window manager is already running on display :0.0.
Blackbox::Bla

Any help would be greatly appreciated

Rick