The first thing you do, if you haven't already, is backup your data while you can, then you can start looking at possible problems.
If you were setup as raid 1 then something has happened to destroy that setup so the best thing you can do, after backing everything up is to reformat and restore the data.
The other thing is that there may be bad sectors on one of the drives that have been remapped by the drive firmware that triggered the e-mail and the strange log entries.
You could also try the paper clip reset to defaults to see if that clears the problem.