Virtual URLs aren't handled well at all (with the exception of the couple of modules that are served by the user group serve routine) in older versions of the ACS, including 3.2, the ACS Classic (Oracle) version that OpenACS was ported from.
Short term ... well, how much work do you want to do? It is possible you're seeing behavior unique to the OpenACS version, but probably not . I've not used abstract URLs on my existing ACS 3x sites except in the "groupified" modules so can't be of any help in estimating how much work would be involved in implementing the behavior you want.
ACS 4.0 deals with abstract URLs from the ground up, so with this version this kind of behavior should go away.
