Can't create groovy project from existing source code

!ENTRY org.eclipse.jdt.ui 4 0 2014-04-10 10:32:05.633
!MESSAGE Error in JDT Core during AST creation
!STACK 0
java.lang.IllegalArgumentException
	at org.eclipse.jdt.core.dom.ASTNode.setSourceRange(ASTNode.java:2845)
	at org.eclipse.jdt.core.dom.ASTConverter.setTypeAnnotationsAndSourceRangeOnArray(ASTConverter.java:3488)
	at org.eclipse.jdt.core.dom.ASTConverter.convertToArray(ASTConverter.java:3234)
	at org.eclipse.jdt.core.dom.ASTConverter.convertType(ASTConverter.java:3696)
	at org.eclipse.jdt.core.dom.ASTConverter.convert(ASTConverter.java:618)
	at org.eclipse.jdt.core.dom.ASTConverter.buildBodyDeclarations(ASTConverter.java:207)
	at org.eclipse.jdt.core.dom.ASTConverter.convert(ASTConverter.java:3026)
	at org.eclipse.jdt.core.dom.ASTConverter.convert(ASTConverter.java:1442)
	at org.eclipse.jdt.core.dom.CompilationUnitResolver.convert(CompilationUnitResolver.java:295)
	at org.eclipse.jdt.core.dom.ASTParser.internalCreateAST(ASTParser.java:1209)
	at org.eclipse.jdt.core.dom.ASTParser.createAST(ASTParser.java:809)
	at org.eclipse.jdt.internal.ui.javaeditor.ASTProvider$1.run(ASTProvider.java:544)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
	at org.eclipse.jdt.internal.ui.javaeditor.ASTProvider.createAST(ASTProvider.java:537)
	at org.eclipse.jdt.internal.ui.javaeditor.ASTProvider.getAST(ASTProvider.java:480)
	at org.eclipse.jdt.ui.SharedASTProvider.getAST(SharedASTProvider.java:128)
	at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$PartListenerGroup.calculateASTandInform(SelectionListenerWithASTManager.java:170)
	at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$PartListenerGroup$3.run(SelectionListenerWithASTManager.java:155)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:53)