Not sure if anyone has come across this, but some times when I try to free some texture memory, my game does a code dump :-(

The textures do exist as I am displaying them on the screen, but for some reason some of them always or after a while dump

Heres the type of code

    if(tex_tiles) free(tex_tiles);

Does anyone have any ideas what might be causing this? or any other things that I should be doing when trying to clear down memory usage.

For a bit more info - This mainly happens when I go between different part of my game (e.g. between game and menu) when I do this I clear down all my game graphics and reinitialise all the menu graphics