When I build the nestest source check out using eclipse,it says as below,I just do as the official document,anybody know why?

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknow n Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Un known Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.limewire.ui.swing.Main.main(Main.java:87)
Caused by: java.lang.Error: Unresolved compilation problem:
The method getFormatString() of type GuiUtils.SpeedUnit must override a
superclass method

at org.limewire.ui.swing.util.GuiUtils$SpeedUnit.getF ormatString(GuiUti
s.java:128)
at org.limewire.ui.swing.util.GuiUtils.<clinit>(GuiUt ils.java:75)
at org.limewire.ui.swing.GuiLoader.load(GuiLoader.jav a:49)
... 5 more