I am also having trouble with emails - being asked constantly to enter password, even though I have ticked "remember my password" and it worked up to a week ago.  Despite re-entering password, the Log-In box keeps appearing and does not let me send or receive emails. I have tried repairing Windows Essentials. The message is as follows:-

Unable to send or receive messages for the O2.co (val.gas) account. An incorrect password was entered. The next time you send or receive messages, you'll be asked to enter your username and password for this account.

Server Error: 0x800CCC90
Server Response: -ERR [SYS/TEMP] mail domain is temporarily unavailable
Server: 'mail.o2.co.uk'
Windows Live Mail Error ID: 0x800CCC92
Protocol: POP3
Port: 110
Secure(SSL): No