I don't have Tk::SplitFrame installed and i don't have time right now to install it and test your code. Also i'm not an expert. But i do have a few comments:
if it starts it is unlikely to be a pack or grid (ie. geometry managment problem).
from your description it sounds as if the "tool-tip" is involved and this is a product of what module? Notebook? How much have you used it before? (I haven't used it at all.)
I do know that when i was trying to perform operations on menu entries independent of activating them (this is when things like "tool tips" sometimes apply; but it sounds like this is not a menu context -- or is it?) I ran across a lot of web records by people regarding the problems with doing this and that there was some consensus about some modules also failing with "tool tips"
So it may really be a problem in a module that you are kicking yourself over. Or some more knowlegable person may come along. I believe zentara knows a lot of Tk and perhaps uses windows.
Also: are you sure you have isolated your problem as much as you can before you ask someone to solve it? I don't need a demo of your app on any level...