Tested on: OSX 10.4 (JDK 1.5) and Windows XP (JDK 1.6)
Scala version: 2.3.3

I have two programs, almost identical. The first one is compiled with scalac and run with "scalac generic1.scala; scala RunMe".

----------------- generic1.scala ----------------------
abstract class A[T] {
  def myVal: T
}

class B[T](value: T) extends A[T] {
  def myVal = value
}

object RunMe extends Application {
  Console.println(new B[int](23).myVal)
}
--------------------------------------------------------------

The second one is run in script mode, "scala generic2.scala"

----------------- generic2.scala ----------------------
abstract class A[T] {
  def myVal: T
}

class B[T](value: T) extends A[T] {
  def myVal = value
}

Console.println(new B[int](23).myVal)
--------------------------------------------------------------