Syncing iCal Data

We have two Macs, two iPads and one iPhone which have the Calendar application synced together. Syncing events was worked quite well until recently. Now syncing between all devices except one iPad continues to work fine, however events entered on that iPad do not show up on the other devices. Curiously, events entered on one of the other devices do sync to the errant iPad, but nothing entered on it appears on any of the other devices. Other apps like mail and contacts sync ok between all devices. I have reset the settings on the problem iPad and checked the iCalendar and iCloud setting against the setting on the other devices finding no differences. Can anyone help me with this problem? I would appreciate any assistance on solving this mystery!