There already appears to be an X server running on display :0

[Johannes Pilkahn]

My Karmic's been acting up during boot-up lately. Instead of showing me 
the login screen Im presented this message:
"There already appears to be an X server running on display :0. Should 
another display number be tried? Answering no will cause GDM to attempt 
starting the server on :0 again. (you can change consoles by pressing 
Ctrl-Alt plus a function key, such as ctrl-alt-F7 to go to consoles 7. X 
servers usually run on consoles 7 and higher.)"
Offers "Yes" or "No" option.
Hitting Yes results in: "The specified display number was busy so this 
server was started on display :1:" and then I hit "Ok" and my login 
screen comes up. Sometimes however, there's another message telling me 
that it is crashing and to hit "Ok: to try another server. And that 
message will keep coming up no matter how many times click "Ok".

Where in my configuration could things be messed up? Stumped, Johannes