NullPointerException is thrown during opening a project. 

For more details see issues:
http://www.netbeans.org/issues/show_bug.cgi?id=103644
http://statistics.netbeans.org/analytics/detail.do?id=65738

(Stack trace is taken from UI Gesture collector XML file)

<exception>
    <message>java.lang.NullPointerException</message>
    <frame>
        <class>org.netbeans.modules.java.project.BrokenReferencesModel</class>
        <method>getReferences</method>
        <line>276</line>
        <file/>
    </frame>
    <frame>
        <class>org.netbeans.modules.java.project.BrokenReferencesModel</class>
        <method>isBroken</method>
        <line>180</line>
        <file/>
    </frame>
    <frame>
        <class>org.netbeans.spi.java.project.support.ui.BrokenReferencesSupport</class>
        <method>isBroken</method>
        <line>110</line>
        <file/>
    </frame>
    <frame>
        <class>org.netbeans.modules.java.j2seproject.ui.J2SELogicalViewProvider</class>
        <method>hasBrokenLinks</method>
        <line>196</line>
        <file/>
    </frame>
    <frame>
        <class>org.netbeans.modules.java.j2seproject.J2SEProject$ProjectOpenedHookImpl</class>
        <method>projectOpened</method>
        <line>579</line>
        <file/>
    </frame>
</exception>