Multiple workspace crashes using Eclipe Indigo

Multiple workspace crashes occurred while viewing the Getting Started Guide examples for AS7. I am not able to reproduce this issue.
As near as I can recall, I did the following:

• Opened the Numberguess example home.xhtml file
• Went to Eclipse help search to search for how to turn on line numbers
• Started to open preferences, but Eclipse crashed.

When I started Eclipse, I got this error message:
An internal error occurred during: "Updating Maven Dependencies". java.lang.ExceptionInInitializerError at org.jboss.tools.common.model.options.PreferenceModelUtilities.getPreferenceModel(PreferenceModelUtilities.java:48)

Eclipse started, but when I tried to open and xhtml file, I got this error:
Problems occurred when invoking code from plug-in: "org.eclipse.jface".
java.lang.NoClassDefFoundError: Could not initialize class org.jboss.tools.common.model.options.PreferenceModelUtilities$PreferenceModelHolder

There is NullPointerException in the error log, although I don't know if it caused the workspace crashes.