Yes, it is the same version of Alfresco. If you look at help ticket 6041, you will see where this is (you may have even helped look into it). We don't know what the problem is but have basically gone done the approach pulling all the children nodes in the webscript, retrieving the custom date parameter and sorting them ourselves.
Basically, the Lucene query would work properly in the authoring environment but in the Runtime environment it would "flip" the first and last entry (if not some more) actually giving us the oldest one first.
We haven't solved this but it has gotten old enough that we've coded away from using Lucene.