This happens with build 2.1.0.nightly-2_09-201201160525-28d3790.

I have the preference (Scala : Organize Imports : collapse into single import statement) selected.
I also have the preference (Java : Editor : Save Actions : Organize imports) selected.

I create a Scala file with,

import scala.util.DynamicVariable
import scala.util.Random

trait Bogus {
  def a: Random
  def b: DynamicVariable[_]
}

When I save the file I expect to see,

import scala.util.{ DynamicVariable, Random }

trait Bogus {
  def a: Random
  def b: DynamicVariable[_]
}

Instead, the imports statements are not changed.
Also, when I manually organize the imports, the import statements are not changed.

Assume I add another import from the same package, for example,

import scala.util.DynamicVariable
import scala.util.MurmurHash
import scala.util.Random

trait Bogus {
  def a: Random
  def b: DynamicVariable[_]
  def c: MurmurHash[_]
}

When I save the file, the import statements are not changed.
However, when I manually organize the import statements, the file becomes,

import scala.util.{MurmurHash, DynamicVariable}
import scala.util.Random

trait Bogus {
  def a: Random
  def b: DynamicVariable[_]
  def c: MurmurHash[_]
}

The imports are not automatically organized when the file is saved.
The imports are not correctly organized when manually organized.