On 12/16/15; my email acct. through WLM started asking me for my log on credentials - username & password. I have had this set up for 3 yrs., w/out having this box popping up until the 16th. I enter the info., & it just keeps popping up. If I cancel out I get

"Unable to send or receive messages for the XXX account. An incorrect password was entered. The next time you send or receive messages, you'll be asked to enter your user name and password for this account.

Server Error: 0x800CCC90
Server Response: -ERR [AUTH] (#MBR1212) Incorrect username or password.
Server: 'inbound.att.net'
Windows Live Mail Error ID: 0x800CCC92
Protocol: POP3
Port: 995
Secure(SSL): Yes

My username & pw are correct. All my protocols are correct - I have verified them countless times w/ATT.I have uninstalled & reinstalled WLM; initiated an email repair. I have run security checks. Rebooted, etc...I have spent hours looking at all these diff. forums w/out finding an answer or doing what is suggested. I can log onto my email through a browser. I am at a loss!! Any ideas?