Follow this link and you'll see it here on this forum as well!
 http://www.mambohacks.com/component/option,com_smf/Itemid,57/expv,1/topic,4/prev_next,next

I thought it was only my installation, but it seems to be a general error if smf runs inside mambo!

Any ideas?

This error does not appear if you run the same installation standalone...