FWIW: I posted a patch a while ago that added all such pages to a special category:
http://www.mail-archive.com/semediawiki-devel%40lists.sourceforge.net/msg00481.html

Re-assign to extension developer for triage/comments.

As of SMW 1.4.3, there is a special property "Has improper value for" that records input errors. A special page is not needed, since an #ask query or the Property page of that property can be used to show all pages with errors. The property relates the page where an error occurred to the property that was used for the problematic annotation. This also allows SMW to automatically repair errors when the datatype of a property is changed (if the error was caused by having the wrong type in the first place).