Lion reinstall shows -2,147,438,648 hours remaining

Trying to reinstall Lion, and it's been cooking for nearly 12 hours. It goes down to 3 minutes remaining, then jumps to -2,147,438,648 hours and X minutes (the X varies) remaining...then jumps back to 53 minutes remaining, and repeats. The progress bar is at 100%. This cycle keeps repeating. I'm reluctant to restart during an OS install! Any ideas? Or do I have a time machine that's bringing me back almost 245,000 years?