Jperf Question

Hi. I finally got Jperf running on my WinXP box, and all was working beautifully until this morning. The Jperf software runs, but the bandwidth and jitter graphs will no longer appear. At the end of a test that is setup to automatically have the graph pop up, I get one of the following two errors in the DOS window in which I started Jperf:

Exception in thread "Thread-2" java.lang.NoClassDefFoundError: com/jrefinery/ui
Drawable
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
        at com.jrefinery.chart.ChartFactory.createAreaXYChart(Unknown Source)
        at JperfGUI.createBWGraph(JperfGUI.java:1239)
        at IperfThread.run(IperfThread.java:69)

Exception in thread "Thread-3" java.lang.NoClassDefFoundError: com/jrefinery/ui
Drawable
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
        at com.jrefinery.chart.ChartFactory.createAreaXYChart(Unknown Source)
        at JperfGUI.createBWGraph(JperfGUI.java:1239)
        at IperfThread.run(IperfThread.java:69)

Prior to this morning (no system or network changes btw), the graphs worked just fine for any test that I ran. All the jar files are in the same directory as iperf.exe, and I start Jperf with the following: