I just got the OTA update to Froyo, and discovered that I can only send email from my gmail address. On the gmail web client, and on 2.1, gmail automatically uses my alternate address (i.e., "email@example.com"). Since the update, I only have access to "firstname.lastname@example.org". I do have two gmail accounts set up -- and can switch back and forth between them. I'm tempted to try deleting that account from the phone and re-adding it, but since it's my primary google account for my phone, I'm not sure what other problems may be created.