It appears warmux exhibits lots of issues with that version of sdl_gfx. We have someone reporting backtraces of crashes leading to sdl_gfx. In addition, it might be responsible of memory corruption leading to crashes already experienced by a nixos user:
https://gna.org/bugs/?17768
In any case, valgrind confirms the out-of-bound accesses.

I would suggest to bump the sdl_gfx version to 2.0.22, as requested by its author for ubuntu:
https://bugs.launchpad.net/ubuntu/+source/sdlgfx/+bug/676799
and myself for debian:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=616409

If you have a strict policy on versioning, you may want to look at this commit that I suspect to fix the issue:
http://sdlgfx.svn.sourceforge.net/viewvc/sdlgfx?view=revision&revision=35

Thanks

Submitted on 4 March 2011 at 19:49