UV problem on mirrowed objects


I stepped on this problem while doing some AO baking. When I bake an object that’s a mirror of the original UV mapped object, the texture end up completely black. The workaround I found is to flip the object normals, so they point to the inside, bake, then flip normals again. Even trying to mirror the UV map of the new object or scale it by -1 on the X direction didn’t help.

The normals of the new object are right after I mirror it, but it looks like the mirroring process is causing some trouble with the vertex order or something like that. Is there any way to fix this?
I’m new to blender and to this whole modeling thing :o I hope it’s not a too lame question. Thanks.

PS: Sorry about my english.

Humm, thinking again about it, isn’t that a bug?