Backing up iPad to iCloud problem

This may be caused by a corrupt existing backup that needs to be deleted, or by data on your phone that is preventing the backup. To troubleshoot these, try deleting your last backup (if you have one) by turning off iCloud Backup in Settings>iCloud>Storage & Backup, then tap Manage Storage, swipe across your backup and tap Delete, then go back and turn iCloud Backup back on again. If it still won't back up, you may have an app that is preventing the backup from succeeding. To locate which one, go to Settings>iCloud>Storage & Backup>Manage Storage, tap the name of your device under Backups, under Backup Options tap Show All Apps, then turn them all to Off (including camera roll) and try backing up again. If it succeeds, then the camera roll and/or one of your apps is preventing the backup and you'll have to located by process of elimination. Turn the camera roll On and try backing up again. If it succeeds, turn some of your apps to On and try backing up again. If it succeeds again, turn some more apps to On then try again; repeat this process until it fails. Eventually you'll be able to locate the problem app and exclude it from your backup.

It may also be caused by network connectivity to the iCloud server. Solutions to that include power-cycling your wireless router (unplugging it for 15 seconds, then plugging it back in), resetting network settings on your phone (in Settings>General>Reset), updating the firmware on your router, and changing the router's DNS settings to use Google's public DNS (see https://developers.google.com/speed/public-dns/docs/using).

There may be something corrupt on your iPad. Try connecting it to your computer, open iTunes, click on the name of your iPad in iTunes, then look at the capacity bar at the bottom. How large is the "Other" segment? (You'll have to hover your mouse over it to see how large it is.)