GWT doesn't work in eclipse

I upgraded GWT to the latest version (2.2.0), but I can't run my
project (created with GWT 2.1.0). I receive this error:

-----------------------------------------------------------------------------------------------------------------------------------------
Unable to load server class
'com.google.appengine.tools.development.gwt.AppEngineLauncher'
java.lang.ClassNotFoundException:
com.google.appengine.tools.development.gwt.AppEngineLauncher
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at com.google.gwt.dev.DevMode$ArgHandlerServer.setString(DevMode.java:
111)
at
com.google.gwt.util.tools.ArgHandlerString.handle(ArgHandlerString.java:
26)
at com.google.gwt.util.tools.ToolBase.processArgs(ToolBase.java:238)
at
com.google.gwt.dev.ArgProcessorBase.processArgs(ArgProcessorBase.java:
29)
at com.google.gwt.dev.DevMode.main(DevMode.java:303)
Google Web Toolkit 2.2.0
-----------------------------------------------------------------------------------------------------------------------------------------

I don't know which SDK to install, I have a few files calles gwt-
user.jar . I tried all of them but it doesn't work.

Thanks,
Uri Even-Chen.

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