I had this issue with a brand new ipad3. Took it back to store and they exchanged it for a new one. Out of the box the new has the same issue. It was not caused by any downloaded app because I set the new machine up from scratch without downloading any apps. After much research got a workaround by not adding any email accounts or using icloud. The ipad has been OK since I took these steps. I can access email using hotmail on safari. Not ideal but works. Maybe a future OS upgrade may resolve or any suggestions welcome.
Ps did hard/soft resets reinstalled from backups via icloud/itunes -nothing worked