I donwloaded a sample and this is how it looks:
http://i49.tinypic.com/de2ngm.png
It's helpful?
It depends on if this is using the wxAUI toolbar. As you know, there are also other (including the default wxToolbar) toolbars around. So the question is, is this a sample for wxAUI?
I you are unsure but have the sources of wxWidgets, I guess the easiest way would be to compile the wxAUI sample of your wxWidgets version (usually in [wxWidgets_src]\samples\aui) for verification. This should be really easy, espeicially if you self-compiled wxWidgets anyways.
Also keep in mind that this must match the wx version you are using. So don'T trty samples compiled against wx2.9.x if you are using wx2.8.x.
For me (btw) I don't see such artefacts on Linux.