Compiling GWT source code - [ERROR] Unable to find class java/lang/Object

Would anyone know what is the usual culprit of this when trying to compile GWT from source?

D:\gwt\trunk>ant

...

gwtc:
     [java] Compiling module com.google.gwt.sample.dynatable.DynaTable
     [java]    Ignored 79 units with compilation errors in first pass.
     [java] Compile with -strict or with -logLevel set to TRACE or DEBUG to see all errors.
     [java]    Resolving com.google.gwt.cell.client.FieldUpdater
     [java]       Found type 'com.google.gwt.cell.client.FieldUpdater'
     [java]          [ERROR] Unable to find class java/lang/Object

...and more of these follows

I went through these steps: Compiling from Source

D:\gwt\trunk>java -version

java version "1.7.0_07"

Java(TM) SE Runtime Environment (build 1.7.0_07-b11)

Java HotSpot(TM) 64-Bit Server VM (build 23.3-b01, mixed mode)

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