If no one else has this problem, how do I fix it on my computer?

Inserting the group name in the bcc slot still does not work. However, I have discovered that I can add each email address individually and the message can then sent. To do this, I hold down the Shift key and check the little circle on the left of each name. Below the list of names there is a place to click "send to the bcc list" (or something to that effect). All fifty or so email addresses then appear in the bcc address list and the email can be sent to all of them. This is very cumbersome, so I hope thunderbird will soon fix the problem and accept just the name of the group in the bcc slot.