I don't know what this supposed to do, but after loading en getting the metatable, it seems there are only functions in the metatable.
Then you take the metatable of all keys which is bound to give the string table, since they are all strings, its gtk2_tab["__index"] for instance.
So i'm not really that surprised.

Now the first error message is a funny one, reminds me a lot of windows
perhaps you pass it a wrong type of userdata?

greetz,

Jan-Pieter