mod_security and No Permission Page

[Digital Jedi]

Earlier this week, I was making some changes to one my clients websites and, for no apparent reason, I was blocked by a firewall. Turns out I was blocked from all my websites on my host's servers. I got them to lift the firewall within a few minutes and went back to work, and the very first options I tried to save gave me the no permissions error, essentially like the one below.

Forbidden

You don't have permission to access /forums/admincp/automediaembed_admin.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

After working with them for a few days, I don't have any idea why this is happening, but it seems to be only happening with modifications, not vB core functions, but on every site I have vB installed (mine, my demo board and my client's website), and only when saving certain functions. They assure me that all my permissions are set, that mod_security has not logged any errors from any of my domains and that it's a vBulletin issue (3.8.5 or lower in all cases).

Specifically, what I've encountered is not being able to save settings where certain characters are being saved. For example, AME let's me save definitions that have RegEx patterns it uses to identify URL strings. I couldn't make any changes to those definitions until I either (grouped) or [bracketed] the http:// anywhere a RegEx would be saved. It still won't let me delete definitions, even if I blank all the fields. Another modification that lets me save human verification questions in a large form field, but I had to move the individual entries around before it wouldn't finally let me save it.

This doesn't seem to be a specific mod problem, but possibly a PHP problem. It's decidedly not a CHMOD issue. That the first thing I checked. I don't know what else to ask my host to look for to try and root out why I'm still having trouble. I do know that at least one setting let me get so far when trying to delete entries in a modification, but suddenly started denying me the first step. Is my forum just out of date? Are my mods just too old for PHP5? Or is it really mod_security that's the issues, and I have to figure out how to convince my host of that?