Yahoo POP Account in Outlook 2007 stopped working?

Recently my Outlook 2007 POP Account with Yahoo Plus stopped sending emails out. I get a "task yahoo email - sending reported error (0x80070057) could not complete the operation. One or more parameter values are not valid". It was working fine a few weeks ago and when I checked my settings are still the same. I am using incoming server pop3 995 and outgoing SMTP Server 465 (ssl). Any help will be appreciated. Many tks