Hi Alexander, i got the same problems to activate and get a running nagvis after installation under squeeze. Sorry, solving that issue is beyond my ken.
In my estimation i think this trouble is associated by using ndoutils as backend. Do you have any plans to implementate livestatus as backend for nagvis or do you know any projects which solve the probs in debian; alternatively is there any documentation/debian-package of livestatus under debian? Thanks in advance. Best wishes, Nikolas Braun