Yes, the system_health extended event is available in 2008 r2. I'm looking at the results from it now. It's not easy to follow what'ss going on. I did find...

I think this is what you want to do.

http://www.sqlservercentral.com/articles/Administering/implementing_efs/870/

I would look at encryption first. Is this on 2005?

Can you post your table and query? Sample data would help.

Can you try a restore from one of the older backups? One from before you added the new tables. That may help narrow down the problem.