WDSC won't open

One of the developers in my shop couldn't get WDSC to open this morning. The 
splash screen shows up, but then it disappears and message window appears 
saying to check the .log file in .metadata.  Here is what the log file says:

!SESSION ----------------------------------------------------------------------
!ENTRY org.eclipse.core.launcher 4 0 Dec 15, 2004 09:07:48.864
!MESSAGE Exception launching the Eclipse Platform:
!STACK
java.lang.reflect.InvocationTargetException: java.lang.RuntimeException: Fatal 
Error: Unable to locate matching org.eclipse.core.runtime plug-in.
        at java.lang.Throwable.<init>(Throwable.java:54)
        at java.lang.Throwable.<init>(Throwable.java:68)
        at 
org.eclipse.core.internal.boot.PlatformConfiguration.locateDefaultPlugins(PlatformConfiguration.java:2264)
        at 
org.eclipse.core.internal.boot.PlatformConfiguration.<init>(PlatformConfiguration.java:903)
        at 
org.eclipse.core.internal.boot.PlatformConfiguration.startup(PlatformConfiguration.java:1368)
        at 
org.eclipse.core.internal.boot.InternalBootLoader.initialize(InternalBootLoader.java:582)
        at 
org.eclipse.core.internal.boot.InternalBootLoader.startup(InternalBootLoader.java:1035)
        at 
org.eclipse.core.internal.boot.InternalBootLoader.run(InternalBootLoader.java:838)
        at org.eclipse.core.boot.BootLoader.run(BootLoader.java:461)
        at java.lang.reflect.AccessibleObject.invokeL(AccessibleObject.java:207)
        at java.lang.reflect.Method.invoke(Method.java:271)
        at org.eclipse.core.launcher.Main.basicRun(Main.java:291)
        at org.eclipse.core.launcher.Main.run(Main.java:747)
        at org.eclipse.core.launcher.Main.main(Main.java:583)

What do I need to do to resolve the problem?

Thanks,
Kelly