I know this is a bit old but I was wondering were you able to solve this issue? I am currently having a similar issue with a Validator class.
I have a SLSB backing implementing the validator intefrace and I get a similar issue. Any help would be great.
I dropped this matter because I managed to solve my task without the use of a converter.
Make sure all validator/converter classes are on the classpath of the war (putting them in the ejb jar doesn't work)
I've got to test that next time I need a tailor made converter.