Looked at the link you provided, don't know how that resolves the problem, because it is still not working.
I have installed pfSense v1.2.2, reinstalled squid and squidguard packages, installed blacklists, and checked to make sure squidguard was working correctly.
However, once you try to add the rewrite info for Google SafeSearch it blows out, defaults to different web admin theme, loses all package settings and base configuration. Cannot re-load from backups either. If you close and reopen the browser, it won't even let you access the web console.
The only way you're going to see this problem and understand it is for you to try doing it on a system.
Your response to BobFather is the same one I'm trying and it's not working.
"Use 'Rewrite' item for define Google safe search rule"
Must be added as
Target URL = (google..*/search?.*q=.*)
Replace To URL = \1\&safe=active
Thanks for the feedback.