The solution: Hold down the Option key when you launch Emailer. A dialog box will appear giving you the option to rebuild the Emailer database (this database is a new feature of Emailer 2.0; 1.x versions stored each message as a separate file on your disk - which could take up an enormous amount of disk space if you get as much mail as I do!). Anyway, rebuilding the database did the trick for me. The message and the Type 11 errors were gone when the program finally opened!
b. When trying to solve this problem, I tried to open Emailer 2.0 with all extensions off. It would not open. Instead I got a message that said Emailer "cannot be opened because an unexpected error occured." I have since learned that this is because Emailer needs ObjectSupportLib to open and that OSL is functionally disabled when you start up with extensions off. The Finder does not properly recognize that this is the case and so gives the general error message.