I am having the same lockup problem, but pressing c1 and c4 doesn't help. I have to wait a day and totally discharge the battery. It's very anoying!!!!
To change your email settings (unsubscribe, digest only, or vacation mode): http://senderogroup.com/email.htm Additionally, to unsubscribe send an email to gps-talkusers-request@xxxxxxxxxxxxx with "unsubscribe" in the Subject.