But I think the following is indeed the case: "Sometimes Yahoo is the problem, try waiting an hour and try to login again by going to mail.yahoo.com."
The problem is on my pc as well as on my ipod. And I've tried different browsers and switched between 'basic mail' and the other one.
Will try again tomorrow and if the problem still occurs, then I'll contemplate going to a different e-mail service, because this is not the first problem I've encountered with yahoo mail in the last months.