Popup message "to protect you your account has been suspended for up to 48 hours" when trying to send mail

I wanted to see what the difference was between Yahoo Premium services and the free account to decide if I should switch to GMail, so I cancelled my premium service. I promptly received a popup message "to protect you your account has been suspended for up to 48 hours" when trying to send emails. While 48 hours suspension for no reason and with no resolution given may sound reasonable to people who don't use their email for work, this is unacceptable to those of us who do. I've had no similar problems in the past so will wait 24 before packing up my account to GMail.