build.sbt

libraryDependencies ++= Seq(
  "net.databinder" %% "unfiltered-filter" % "0.6.5"
 ,"javax.servlet" % "servlet-api" % "2.5" % "provided"
 ,"org.eclipse.jetty" % "jetty-webapp" % "7.6.8.v20121106"
)

scalaVersion := "2.10.0"

errorlog.txt

[error] (run-main) java.lang.VerifyError: (class: Server, method: <init> signature: ()V) Expecting to find object/array on stack
java.lang.VerifyError: (class: Server, method: <init> signature: ()V) Expecting to find object/array on stack
        at Main$.<init>(Main.scala:4)
        at Main$.<clinit>(Main.scala)
        at Main.main(Main.scala)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
[trace] Stack trace suppressed: run last compile:run for the full output.
java.lang.RuntimeException: Nonzero exit code: 1
        at scala.sys.package$.error(package.scala:27)
[trace] Stack trace suppressed: run last compile:run for the full output.
[error] (compile:run) Nonzero exit code: 1

Main1.scala

import unfiltered.response._

object Main extends App{
  new Server
}

class Server extends unfiltered.filter.Planify({
  case _ => ResponseString("hello")
})

Main2.scala

import unfiltered.response._

object Main extends App{
  new Server
}

class Server extends unfiltered.filter.Plan{
  def intent = {
    case _ => ResponseString("hello")
  }
}

I have the same problem, did you find a solution?