Referrer error

[Spug]

YaBB SE Version: 1.5.5
PHP Version: 4.3.4
MySQL Version: 4.0.x

Problem Description:
Seems many people have problems with this, according to the posts here... Well, here, it consists of members not being able to delete their own posts. I can delete posts, being an admin, but members can not. They get the 'invalid referrer' error. I also tried registering as a member, and I can delete posts just fine.

I do not get this error anywhere, I do not use any shorturls.

Is it possible that this is caused by the members' firewalls? I've heard of that before, I think, on some other site... That Norton Internet Security / Norton Personal Firewall blocks referrers by default... I don't know if all those members use Norton, though, but I'll check. Just thought I'd mention it, so the moderators here (who clearly didn't know about this before) can look into it

[[Unknown]]

This can be caused by anything, but it's main causes are redirection (like shorturl) and frames.  The idea is, if a referer is sent that is wrong, you'll get this error.  This is done for security, and without it I could hack your board EASILY.

-[Unknown]