When I use NetBeans for almost any task (in particular, attempting to open a project), a red minus sign in the bottom right corner of the IDE starts blinking and I get the following NullPointerException error when I click it. Unfortunately I cannot reinstall NetBeans since I am using a shared computer lab account.

java.lang.NullPointerException
    at org.openide.util.Exceptions.attachMessage(Unknown Source)
    at org.netbeans.modules.project.ant.Util$ErrHandler.annotate(Unknown Source)
    at org.netbeans.modules.project.ant.Util$ErrHandler.fatalError(Unknown Source)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:388)
    at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1414)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:925)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:807)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:225)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:283)
    at org.openide.xml.XMLUtil.parse(Unknown Source)
    at org.netbeans.modules.project.ant.AntBasedProjectFactorySingleton.loadProjectXml(Unknown Source)
    at org.netbeans.modules.project.ant.AntBasedProjectFactorySingleton.loadProject(Unknown Source)
    at org.netbeans.api.project.ProjectManager.createProject(Unknown Source)
    at org.netbeans.api.project.ProjectManager.access$300(Unknown Source)
    at org.netbeans.api.project.ProjectManager$2.run(Unknown Source)
    at org.netbeans.api.project.ProjectManager$2.run(Unknown Source)
    at org.openide.util.Mutex.readAccess(Unknown Source)
    at org.netbeans.api.project.ProjectManager.findProject(Unknown Source)
    at org.netbeans.modules.project.ui.OpenProjectList.fileToProject(Unknown Source)
    at org.netbeans.modules.project.ui.ProjectChooserAccessory$ProjectFileView.run(Unknown Source)
    at org.openide.util.RequestProcessor$Task.run(Unknown Source)
[catch] at org.openide.util.RequestProcessor$Processor.run(Unknown Source)

I have recently had problems with going over my disk space quota on this computer lab account. I cleaned up my files and I now have about 10MB free. I'm not sure whether or not this is related to the problem with NetBeans.