Dear Andrew, thanks a lot for your reply. I'm afraid the memory leak or, if you want, the continuos growth of the memory occupied by the combination Aolserver/OpenACS does not depend on my particular application. Just install OpenACS, move around some few pages (try for instance the included test pages) and have a look at the memory occupation.... you'll see that it is growing. So this is an endemic behaviour of the infrastructure and not of the particular applications put on top of it.
Cheers and thanks,
Maurizio