This bug was originally marked as duplicate of bug 218475, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.

Build: NetBeans IDE 7.3 Beta (Build 201210011125)
VM: Java HotSpot(TM) 64-Bit Server VM, 23.3-b01, Java(TM) SE Runtime Environment, 1.7.0_07-b10
OS: Linux

User Comments:
lehel: webclient testing with following the test specification:
http://wiki.netbeans.org/TS_73_HTML5Project
-step: "Create project with standard template":

     Invoke New Project dialog
    select HTML/JavaScript and HTML5 Application
    In the 3rd step Site Template, select Download Online Template
    Select HTML5 Boilerplate and check template's description below
    Press Next
    In the JavaScript Libraries step, there are already selected some libraries that are bundled with the template. Check that you cannot remove them
    Use text field next to Available to filter list of libraries
    Select e.g. Dojo and click to the Version column. List of available versions of Dojo is offered, pick some and add it to the project
    Change Libraries Folder to "js/libs_custom" and finish the process

VALERE91: I just click on next after added JQuery UI librairies in a HTML5 project with Initializr:Bootstrap template

GUEST: setting up a project




Stacktrace: 
java.lang.AssertionError
   at org.openide.loaders.TemplateWizard.updateState(TemplateWizard.java:745)
   at org.netbeans.modules.project.ui.NewProjectWizard.updateState(NewProjectWizard.java:71)
   at org.openide.WizardDescriptor$10.run(WizardDescriptor.java:1445)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1454)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2036)