Gu - Thanks; I never tested it with multi-value properties - hopefully I can try it out at some point and see what the problem is.

Temlakos - it's odd that the code causes regular #ask queries to not work... my guess is that it's due to the hook processing, which is somehow failing in MediaWiki 1.12 - I've only tested it in MW 1.13 and 1.14. Unfortunately I can't think of a solution, short of waiting to see if other people have the same problem in MW 1.12 or earlier and are able to debug it.