Drat

Patch for Fairy/Pixie-related terrain and crashing issues in Dungeon Siege. If a Fairy or Pixie restores a character's health or mana, the player may subsequently encounter missing terrain, and game crashes. The file disables the abilities of both creatures. Extract fairyfix.dsres to <path-to-game>\Resources
 
This is a prevention, not a cure; it won't fix the problem after it happens. To fix an existing problem, follow the instructions here.
 
Found here: http://ds.gemsite.org/web/index.php/patch/GET/detail-5