Is this during the installation process? Is your BoutCheetah working? Is there even a problem or does it just come up with the error without any side effects? Did you install the game from a mirror or from somewhere else? If you did they could be outdated or something. Also try checking the file path (C:\Zylon Gaming\BoutCheetah\data\ui\ui_minimap500.tga) If there is nothing there then you can ask me or someone to send you the proper file. There might have been a zylon gaming folder left over from the last time you played and it had some files in there that shouldn't of been. Hope this helps, post back if the problem isn't resolved.
Edit: Just found out that the file that is corrupt is the ui (background lobby image) for the training camp level, level 6 in sector or the PvP version of the level I'm not really sure. If it won't let you play because of this just ask me to send you the file.