Ultimate Branding not working

Hi,

I've got Ultimate Branding working in 2 different wordpress multisite installs.
Now, I've installed it in a third one, but this time is a single wordpress install with Buddypress. All updated to the last versions.

When I activate the plugin and click Branding->Admin Bar or Branding-> Images, or whatever, I have a wordpress error telling "Are you sure you want to do that? Please try again" (translated from spanish).

Here's an screenshot: https://img.skitch.com/20120917-d2a2e2pmjfm1bi1kkuap46g8yc.jpg

Any help? I've tried with a previous version of the plugin, but also doesn't work.

Thanks.