smart group not working

I have had to create two smart groups, 1 and 2. When I send out a group email I have to keep the numbers under 500 due to server limitations, so I have divided my list in two to wait an hour between mailings.

Group 1 mails fine when I enter "Group 1" in the Bcc section of the email. Group 2 does not work as when I write Group 2 I cannot hit return and it work.

Any ideas why this second group does not work?

Thanks in advance!