I've been using Time Machine over wifi and have had a recurring problem with corrupted sparsebundles. The scenario is a relatively new Airport Extreme, a MacBook with Leopard, and a partitioned Western Digital drive hooked up via USB to the Airport.
The backups work fine, if I'm just around the house, or if I remember to stop Time Machine and give it a few minutes to wind down before leaving. But if I just close the computer and run out the door, and am away from the network when I wake the computer, I come home to a corrupted backup, which generally cannot be repaired with Disk Utility (once or twice Disk Utility has been able to fix it).
This has forced me to delete my entire backup and start from scratch on several occasions. Is there any way around this problem, other than being vigilant about stopping backups before I leave?