I have some further info.
This issue does not seem to have anything to do with the options when customising the toolbar.
It is the position of the tool bar.
Try moving the various toolbars up and down. You should see what I mean.
In fact I can cause the problem to occur by moving the item context toolbar around to some positions.
Basicaly with the problem occuring I resize the GW window then move the main toolbar (with the formative icons) to the bottom. Close GW. Open and move back to the top. Close GW. Problem goes away. (Untill you move some toolbars around again)
Hope this helps.