You need to rebuild the bitfields by going vBulletin Options -> Rebuild Bitfields. But before you do that, make sure to upload all of the files.

I'm sorry but are you sure the option "Rebuild Bitfields" exists the the vBulletin options list box?
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I cant find it?

It should be on the left (in the menu), and the debug mode needs to be turned on.

Oh, then how do I set it to the Debug mode?

Never mind that, instead go to the following URL:

http://www.site.com/path-to-forum/ad...buildbitfields

ok, did that, but then I go to usergroups manager, choose Administrator and I get this warning

Then it's caused by another hack that you may have installed incorrectly.

you are right, I uninstalled the advancedbbcodesettings one and the warning went away!

As you can see I'm logged in as Administrator, created a test user and want to issue a warning to him (lets pretend his post is innapropiate). Isn't the option suposed to appear in the popup links?

Yeah, but you need to correctly configure permissions for both groups (can be warned for the group being warned, can issue warning for the group issuing the warning).