This is what happens when classes folder doesn't exist in project root
(regardless of target or target/classes folders)

s:\workspace2012\leiningen>lein with-profile release uberjar
Performing task 'uberjar' with profile(s): 'release'
Compiling leiningen.core.classpath
Compilation failed: java.io.IOException: The system cannot find the path specifi
ed, compiling:(leiningen/core/classpath.clj:1)
Uberjar aborting because jar/compilation failed: Suppressed exit
Error encountered performing task 'uberjar' with profile(s): 'release'
Suppressed exit


This is what happens when classes folder exist in project root and it's empty

s:\workspace2012\leiningen>lein with-profile release uberjar
Performing task 'uberjar' with profile(s): 'release'
Compiling leiningen.core.classpath
Compiling leiningen.core.eval
Compiling leiningen.core.main
Compiling leiningen.core.project
Compiling leiningen.core.ssl
Compiling leiningen.core.user
Compiling leiningen.core.utils
Compiling leiningen.check
Compiling leiningen.classpath
Compiling leiningen.clean
Compiling leiningen.compile
Compiling leiningen.deploy
Compiling leiningen.deps
Compiling leiningen.do
Compiling leiningen.help
Compiling leiningen.install
Compiling leiningen.jar
Compiling leiningen.javac
Compiling leiningen.plugin
Compiling leiningen.pom
Compiling leiningen.repl
Compilation failed: java.lang.ClassNotFoundException: clojure.tools.nrepl.transp
ort.Transport, compiling:(clojure/tools/nrepl/transport.clj:16)
Uberjar aborting because jar/compilation failed: Suppressed exit
Error encountered performing task 'uberjar' with profile(s): 'release'
Suppressed exit