Re: Contact Us page Feature
The fact that you can view it with admin but not anyone else suggests a permissions problem. However the fact that you're not getting any "You don't have permission" messages contradicts this. Typically this kind of weirdness occurs when the Tiki cache (not browser cache) needs clearing, but I'm assuming you've already done that as suggested. Also, have you set the "Contact user" username (which is above "Allow anonymous users to contact us" under General/Admin? I don't think you need to do this but perhaps you should set an email address for the user that will be contacted too, and make sure that user's information is "public" (under user preferences).
Have you tried using a different theme? Unlikely to be the cause of the problem but always worth ruling out.
The only other thing I can think of is that a template or file pertaining to the the contact feature is corrupt or the incorrect version. You could try downloading the Tiki installation package, extracting the files pertaining to the contact page and re-uploading them to your site.
probably tiki-contact.php and templates/tiki-contact.tpl.
Otherwise you've got me stumped. I've tried reproducing it and I can't (changing various settings and removing permissions etc).
Sorry.