I had a similar instance last year; 15,472 download requests in less than three hours, followed by 32,083 over a five hour period the following day, all for the same file from the same IP address. Fortunately it was a small file, but the site must have been virtually unusable while that was going on, and I never did find out what caused it. That IP still has the dubious distinction of being the only one barred from my site. Want to compare IPs? >:]