I am at the end of my game (or so I think) and I have found every puzzle except the one before the cave (the box). I keep getting an error message and then the game shuts down: Access Violation at 0x004057D7 tried to read from 0x0685A08C. is there anything that I can do about this.

That error/crash appears to be a problem caused by the digital rights management "wrappers" that some game portals use. Please submit a support form with your name, the details of where you bought the game, and the error codes you receive, and you'll be given instructions for a workaround.