NSInvalidUnarchiveOperationException: 'Could not instantiate class named _UITableViewCellSeparatorView'

I was getting the same error after updating to Xcode 5.1.

I was able to get rid of the error by editing the xib for my custom cell.

Under Interface Builder Document in the file inspector, I switched "View as" to "iOS 6.1 and Earlier". I also have "Builds for" set to "iOS 6.0 and Later".