1.6 - Verify Error - AbstractResourceStreamWriter

[Douglas Ferguson]

java.lang.VerifyError: (class: com/visiblehealth/ui/admin/reports/SQLReports, 
method: generateReport signature: 
(Ljava/io/File;)Lorg/apache/wicket/core/util/resource/AbstractResourceStreamWriter;)
 Wrong return type in function
        at java.lang.Class.getDeclaredConstructors0(Native Method)

Anybody else seen this before?

This is my code:

                                                AbstractResourceStreamWriter 
resourceStream = generateReport(file);
                                                String fileName = 
file.getName().replaceAll(".sql$", ".csv");
                                                ResourceStreamRequestHandler 
resourceStreamRequestHandler = 
                                                                new     
ResourceStreamRequestHandler(resourceStream, fileName);
                                                
getRequestCycle().scheduleRequestHandlerAfterCurrent(resourceStreamRequestHandler);

with generateReport:

        public AbstractResourceStreamWriter generateReport(final File file){
                return new AbstractResourceStreamWriter() {
                        private static final long serialVersionUID = 1L;
                        @Override
                        public String getContentType() {
                                return "text/csv;charset=utf-8";
                        }
                        @Override
                        public void write(Response output) {
                                //write my stuff..
                        }

                };
        }