William, If you use more than one email address, the problem may be that you're writing from the wrong one. I get the same error message when I post to a Google group from the wrong address.
Ciao -- You received this message because you are subscribed to the Google Groups "MacVisionaries" group. To post to this group, send email to macvisionar...@googlegroups.com. To unsubscribe from this group, send email to macvisionaries+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/macvisionaries?hl=en.