I've moved this to the gui forum, your question lacks detail, which gui framework and you need to post sample code that shows the problem.
But note that CTRL+TAB (on windows don't know about others) Switches to the next child MDI Child window of a Multiple Document Interface and could be why nothing is happening.
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Windows7, Python 2.7.4., WxPython 188.8.131.52., some Python 3.3