This error normally means that there was a timeout issue with the remote call (e.g. web service).

You can just do a retry and it should work.

However, you might want to review the specific call to see why it is timing out.

The issue which occured is described in KB000510

The problem does only appear when the object’s lifetime within the AppDomain expires after 5 minutes - AND - when K2 objects (data fields or xml) are changed after the expiration.

To check the lease lifetime of a K2 object you can use the following code:

GetLease(K2.ProcessInstance).CurrentLeaseTime

public System.Runtime.Remoting.Lifetime.ILease GetLease (System.MarshalByRefObject obj)
{
 return 
  (System.Runtime.Remoting.Lifetime.ILease) obj.GetLifetimeService();
}

Regards
Patrik