MOSS 2007 and K2.net Studio : object reference not set

I have a MOSS 2007 server on a machine (with the k2.net moss additional components) and a K2.net Server on another machine, in the same AD domain. The development machine is in the same domain with K2 Studio and VS 2003.

I try to use the K2.net Studio Wizard to add a SharePoint Process but I have this error message :

Object reference not set to an instance of an object.

I see my sites when I click the Browse button

Help is welcome...