Azt irtad, hogy
>Which thread is your Tk.mainloop running on. 
>Main-thread? Or sub-thread?
>If Tk.mainloop is running on a sub-thread (e.g. Thread.new{Tk.mainloop}), 
>can you make Tk.mainloop to run on the main-thread?
>If you can, does the same error happen?

It is already the main thread. I've read about this before, so I've
changed my program, so Tk.mainloop is really the last instruction (and
the main thread) in the program.

Gergo

+-[Kontra, Gergely @ Budapest University of Technology and Economics]-+
|         Email: kgergely / mcl.hu,  kgergely / turul.eet.bme.hu          |
|  URL:   turul.eet.bme.hu/~kgergely    Mobile: (+36 20) 356 9656     |
+-------"Olyan langesz vagyok, hogy poroltoval kellene jarnom!"-------+
.
Magyar php mirror es magyar php dokumentacio: http://hu.php.net