Gekko I am in the same boat. Some days it works some days it doesnt. I clear the cache and it works. I dont want to have to keep doing this. Have you notice a delay in sending? Sometime when I send an email it can take a while to send. Especially with an attachment. Now I know sending an attachment takes awhile but a 1MB attachment on a wi fi connection should not take 10 minutes!!
have you tried using the stock email app? That sends faster I have noticed.