Thanks for the hint, with the new SDL.dll the issue is gone, TuxPaint works perfectly.
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Hi István, and all Seems a bug in SDL, as there is already a new version of SDL than the one used in TP 0.9.21, you could try upgrading it to see if it helps. Locate a file called libSDL.dll in the Tux Paint installation directory, rename it to libSDL.dll.back Donwload the latest version of libsdl from http://www.libsdl.org/release/SDL-1.2.15-win32.zip unzip and put in place. Then start Tux Paint and hope for the best. If it still has this problem, you could watch http://sourceforge.net/p/tuxpaint/bugs/160/ to see if some of the suggestions made there works for your problem. Good luck Pere