SuperDev mode - 500 Error

What could cause this error?

After upgrading to gwt 2.6 and idea 13, at startup superdev mode get this error page:

HTTP ERROR 500

Problem accessing /login;jsessionid=1wmax1chspzqv1kh8sfk5sk5tk. Reason:

    Server Error

Caused by:

Compile failed; see the compiler error output for details.

at org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:933)

at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:757)

at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:382)

in the server log:

Dev Mode initialized. Startup URL: 

http://127.0.0.1:8888/sapphir/admin?gwt.codesvr=127.0.0.1:9997

Starting Jetty on port 8888

   [WARN] 

org.apache.jasper.JasperException: Unable to compile class for JSP

at org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:97)

at org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:346)

at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:414)

at org.apache.jasper.compiler.Compiler.compile(Compiler.java:472)

at org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)

at org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)

at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)

at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)

...

in the /login:

http://pastebin.com/1pBgV8z5

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