Air Disk + SL + sleep = corrupt disk image

I have an Airport Extreme (single band N) with a WD 2TB green disk used as a network disk for backups. My desktop has no problems backing up to it because its either on or off. On the other hand laptops that do a backup over the wireless N experience disk corruption after waking from sleep. MBP with 214GB of data was initially backed up which took many hours. After finally completing backups would run on its own with the mounted sparse disk image. I never shutdown the laptop I always put it to sleep just closing the lid. One/two days after the original full backup, backups stopped working. It would just keep saying making backup disk available. Mounting the disk image would fail saying its corrupt so I trash it and start over. It created a new sparse image and did another full backup. Another day later, same sleep problem. I would just close the lid with the mounted disk image but no backup tasks running and the second image became corrupt. Backup would spend hours "making disk available" and end in failure, unable to mount the backup sparse disk image. I moved backups to an external 400GB firewire and had no problems since.

What is the deal with corrupt backup disk images?