I had the same problem this week, and I'm not sure exactly what happened. However, I was using the Gmail calendar and, after some web research, found out that it is NOT backed up by Google, as I thought it was supposed to be.
SO, I started over. I deleted the Google calendar in Gmail completely so there wouldn't be some sort of conflict later, and rebuilt the calendar (took a day or so) directly in the iPad2's calendar.
Then I enabled iCloud syncing/backup. This calendar is much better than Google's, I have to say. And it's comforting to know I can get it back if it disappears.
Later, I switched my contact list from Gmail to the iPad/Apple contacts, again with iCloud backup. It's a bit tricky to do this so I didn't loose my contacts in the process.
Here's what worked for me: KEEPING MY CONTACTS LIST ON MY iPad/iPhone, first I disabled contact syncing in iTunes for both devices and did a sync so I had a backup handy. Then I went onto iCloud.com and deleted ALL contact entries there so I wouldn't end up with duplicates after the iCloud "merge" was checked. Then, I enabled the contact sync for iCloud.
Scared me at first because all my contacts suddenly disappeared from my iPad/iPhone - but a secnd or two later, they reappeared - just perfect.
I still have a Gmail contacts list in Gmail, but will have to enter any changes/additions I make by hand since I don't want it syncing with my iDevices.