[Pacemaker] recourse dos not start with one active node

[jonas]

hi,
I have build a 2 node test cluster on debian 6 withe an IP recourse. If
I start both nodes the IP recourse starts up properly. If i put one node
on standby the recourse migrates to the other, but if one node gos down
the recourse doesn't migrate. Also the resource doesn't start if just
one node boots up. 
Whats wrong with my setup/expectations? 

I'm looking forward to your answers.
Best regards
Jonas