I just got my Inbox receiving mails again, in less than 2 days after I contacted Yahoo via "account-security-help@cc.yahoo-inc.com". That was really fast, considering an total exchange of 6 e-mails (in 3 days) from my first one to theirs one reporting that Yahoo's people were looking at the problem.

The downside is that I never got a reply from my posts at the "contact Yahoo" web page, and only found the e-mail address in this Forum, not in Yahoo's web pages.