I think the problem may be that the OSK skin layer is loading before the embedded sub-window. You could try adding a wait(xxx) in between the Embed() command and the loadskin() command. Start with something huge like wait(5000) and if that works then just reduce the number until it is acceptable.
A better idea however is to just nudge the bottom of the sub-window up (since you can't really see the part of it that is behind the OSK anyway).
Let me know how it goes and if you still have trouble, post the ini file for the sub-window and the OnPressUp/Down= statment that embeds the sub window and loads the OSK.