We had several multi-configuration projects which were working properly on 1.472. Upon upgrading to 1.473 these projects no longer appeared.

I noticed the following in the Jenkins logs:
SEVERE: Failed Loading job foo_bar
java.lang.NullPointerException
at hudson.matrix.MatrixProject.updateTransientActions(MatrixProject.java:431)
at hudson.model.AbstractProject.onLoad(AbstractProject.java:296)
at hudson.matrix.MatrixProject.onLoad(MatrixProject.java:466)
at hudson.model.Items.load(Items.java:115)
at jenkins.model.Jenkins$17.run(Jenkins.java:2492)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:878)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:679)

Let me know if I can provide any further information.