There's a game I like playing with my nephew called City Magnate. It's like a computerized Monopoly, certainly not heavy-duty. After playing for 7-8 minutes, the game will stop cold, unload to the bare desktop and a window pops up with the title message above. What memory--the RAM or the vidcard? It's a 256MB FX5500, nothing fancy, the most recent drivers installed I think (2006). What causes this, and what do I need to do to eliminate it?

P.S.: Happens on the machine in my specs, booted in XP.