I think the problem is that you defined your projects in build.sbtand they don't seem to be visible in the sbt console. At least in the current version of sbt - see this problem and this problem that were actually fixed just a couple of days ago (!)
I found two ways to overcome this limitation.
Use quotes around project id
set version in "projectId" := "some-version"
project/build.scala
build/Build.scala:
import sbt._
import Keys._
object Build extends Build {
lazy val projectA, projectB = project
}
set version in projectA := "1.42-SNAPSHOT .
, build/Build.scala, , - build.sbt . set.