403 Forbidden When Editing Profile

[Slushie]

Hey everyone, I hope someone can help me.

Members on my forum are getting an error message when they try and edit their profile information. After they click the change profile button it gives a
"403 Forbidden" mesaage as the title of the page.
The rest says:
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Forbidden
You don't have permission to access /index.php on this server.

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

Does anyone know what I can try and edit or do, to make this work?
I'm running 1.1.2.

I just have the basic update packages that SMF says I should install when needed.
The only extra mod is the spoiler tag, and it is working fine.

Now, I recently did switch hosts, and it worked fine before, so I'm guessing that's it. But what would be different? What would make it not work now?

[metallica48423]

new host may be using mod_security,

Having problems with mod_security?

Also check the file permissions (try resetting them in the options page of the package manager)