Reversing Journals not auto reversing

Hi

We're trying to post journals with a Category of "Reverse" hoping that they will automatically reverse and (possibly) post in to the following period. In the Journal Setup for AutoReverse we have set the category "Reverse" to both AutoReverse and AutoPost Reversal but, although when creating the journal it does automatically select the journal to reverse in the following period it does not actually reverse it, let alone post it in to the following period. What are we doing wrong? Are there other settings we have to change for this to work?

Thanks

Martin