[Brian]

Connie, it sounds like you may be having the issue talked about in this post: if services are entirely non-functional, it's a Snow Leopard issue. If you have trouble getting those steps to work, you may want to print that post out and head to your local friendly Genius Bar.

Coolie21, if Mail is still unhappy about the mail plugin in 1.7.4, it means that an older one is still installed somewhere. If you open up
~/Library/Mail/Bundles (and the subfolders) do you see a file with "Omni" anywhere in the title?

If so, quit both OmniFocus and Maill, move that file to the trash, and then try reinstalling the clip-o-tron from OF's preferences. (Be sure you're running 1.7.4 when you do so.)