After updating from 1.1 to 1.2 I am experiencing these assertion errors:
java.lang.AssertionError: class hudson.plugins.templateproject.ProxyPublisher$DescriptorImpl must be assignable to class hudson.tasks.BuildStepDescriptor
at hudson.model.Descriptor.<init>(Descriptor.java:235)
at hudson.plugins.templateproject.ProxyPublisher$DescriptorImpl.<init>(ProxyPublisher.java:73)
at sun.reflect.GeneratedConstructorAccessor187.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at net.java.sezpoz.IndexItem.instance(IndexItem.java:149)
at hudson.ExtensionFinder$Sezpoz.findExtensions(ExtensionFinder.java:101)
at hudson.ExtensionList.load(ExtensionList.java:198)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:181)
at hudson.ExtensionList.iterator(ExtensionList.java:112)
at hudson.model.Hudson.getDescriptorByType(Hudson.java:916)
at hudson.triggers.Trigger.checkTriggers(Trigger.java:217)
at hudson.triggers.Trigger$Cron.doRun(Trigger.java:199)
at hudson.triggers.SafeTimerTask.run(SafeTimerTask.java:54)
at java.util.TimerThread.mainLoop(Timer.java:512)
at java.util.TimerThread.run(Timer.java:462)

repeated many, many times and the Hudson Dashboard page is never presented.

disabling (or switching to version 1.1) of the template-project plugin resolves the issue.