Google changed the way the URL for cached content is displayed.
By default, a cached image is now using a format like this:
The URL itself is not decodable in this format and the URL filter has no way of distinguishing it.
You can turn on SafeSearch Enforcement, and that should trigger the search engine to return only "safe" results as dictated by Google's methods.
You can also revert the cache results back to the "Old-Syle" cache results by appending "&sout=1&surl=1" to the requested URL. When doing so, the format of the linked images is displayed in this format and the URl can be scanned for the location of the original site:
http://www.google.com/imgres?imgrefurl=http://pointlessbanter.net/2006/11/22/the -100-most-influential-americans/&docid=GGb24Gcd1YddHM&w=346&h=503&ei=OaaJTu6zJaX g0QHX1tj-Dw&zoom=1&iact=rc&dur=0&page=1&tbnh=171&tbnw=120&start=0&ndsp=39&ved=1t :429,r:0,s:0&tx=62&ty=101
MWG 6.x cannot append the parameters to the URL, but MWG 7 can with a rule like this:
Force old-style thumbnail searches in google Enabled
Applies to Requests: True / Responses: False / Embedded Objects: False
Enabled Rule Action Events Comments Enabled Find q= search parameter
1: URL.Host matches *google.*
2: AND (URL.HasParameter("q") equals true
3: OR URL.Path equals "search"
4: OR URL.Path equals "/custom"
5: OR URL.Path equals "/images"
6: OR URL.Path equals "images/search"
7: OR URL.Path equals "/videosearch")
Continue Set URL =