I was having the problems described at
http://www.nabble.com/Builds-stay-in-pending-state-even-when-there-are-free-executors-td18496331.html
while using 1.232-private (232 plus a couple of patches I submitted) and
following what seemed to work for one of those users, I tried upgrading to latest.

After stopping the server, replacing the .war with the 1.244 war, and restarting
the server, my builds picked up out of the queue, but then failed like so...
(from the console output)

FATAL: null
java.lang.NullPointerException
at hudson.tasks.Ant.perform(Ant.java:124)
at hudson.model.Build$RunnerImpl.build(Build.java:134)
at hudson.model.Build$RunnerImpl.doRun(Build.java:109)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:231)
at hudson.model.Run.run(Run.java:786)
at hudson.model.Build.run(Build.java:84)
at hudson.model.ResourceController.execute(ResourceController.java:70)
at hudson.model.Executor.run(Executor.java:88)

This comes immediately after it finished updating from svn.

java version "1.6.0_06"
Java(TM) SE Runtime Environment (build 1.6.0_06-b02)

running winstone, java service wrapper, on linux.