Default Registration Options - Won't Save

[WorldCraft]

Sorry if this in the wrong place I couldn't see a help forum.

I have (what I consider) to be a serious problem.
Just recently new registrars on my board (www.everypony.com) started having VM's disabled by default. I was unsure why this was at first because I haven't changed any options to do with that or similar but upon checking a new users profile I realised pretty much every single default registration option was turned off and sure enough in 'User Registration Settings'

Yes / No
Receive Admin Emails
Invisible Mode
Display Email
Receive Private Messages
Send Notification Email When a Private Message is Received
Pop up a Notification Box When a Private Message is Received
Save a copy of sent messages in my Sent Items folder by default
Enable Visitor Messaging
Limit usage of Visitor Messages to Contacts and Moderators
Allow vCard Download
Display Signatures
Display Avatars
Display Images
Display Reputation

All the above except Receive Admin Emails was unticked, so I ticked the ones I wanted and hit save. They were unticked again. So I tried it again thinking my browser might've bugged or something. No luck, there still unticked. However if I untick Admin Emails and save it stays unticked and I can retick it and save and it will be reticked successfully but all the rest can't be activated, at all.

Does anyone have any idea what's wrong here? I've disabled registrations it's that bad (for me).

Any help is very much appreciated,

Thanks!

Worldcraft

P.S.

I'm running VB4x (vBulletin 4.1.3 Patch Level 1)