When I try to start the campaigns email queue I have this error:

Query Failed:INSERT into emails set id='d874dc2f-b738-5e4f-51be-456db9d1061d', date_entered='2006-11-29 16:49:02', date_modified='2006-11-29 16:49:02', assigned_user_id='505690f8-a269-b20e-961f-451a1db914d9', modified_user_id='505690f8-a269-b20e-961f-451a1db914d9', created_by='505690f8-a269-b20e-961f-451a1db914d9', name='Informativa Autoplanus USA: We WILL CHANGE the way WOODWORKER WILL PLANE WOOD', date_start='1999-12-31', time_start='23:00:00', parent_type='Leads', parent_id='1a65d83a-0c15-43d9-64d1-4547124b8c25', description=null, description_html=null, from_addr='campaign@garniga.com', to_addrs='Lawrence Brisco', to_addrs_ids='1a65d83a-0c15-43d9-64d1-4547124b8c25;', to_addrs_names='Lawrence Brisco;', to_addrs_emails='lmb@netdoor.com;', type='archived', status='sent', deleted='0'::MySQL error 1062: Duplicate entry 'Informativa Autoplanus USA: We WILL CHANGE the way WOODWORKER WI' for key 2

I can't understand where is the error, because the mysql error text says that the name is a duplicated entry, but the name isn't a key field on the emails table...

Still now the campaign worked fine, but now are freezed up, I deleted the record but the problem still remains.

Maybe is a MySQL bug?
My running version is 5.0.22