Some email providers insist that you enter your username with no spaces and
no CAPITAL LETTERS.  Some insist that you follow it with the part of your
email address starting with @, and some insist that you don't.  Many insist
that
you enter your password with CAPITAL and lowercase letters in the right
places.  Not all email providers are good at keeping users informed when
they
make changes in these requirements.

If this doesn't help, most versions of the Norton antivirus program
eventually
cause assorted problems in Windows Mail, but this often takes months.
Just disabling the antivirus programs seldom helps; you often have to
uninstall them instead.  You often then need to run this cleanup program,
to take care of what the uninstall left behind:

<http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2005033108162039>

You may even have to remove your email account under Windows Mail,
then restart Windows Mail and add the account again.

http://www.virginmedia.com/help/compatible/

If this cures your problem, you may want a replacement antivirus program
that doesn't cause such problems in Windows Mail.  Most versions of the
McAfee antivirus program and a recent version of the Trend antivirus
program are bad choices; they also cause problems in Windows Mail.
I recommend either avast! or AVG, either one with a custom install that
tells it to leave out the part that scans email.

http://www.avast.com/eng/avast_4_home.html

http://free.grisoft.com/ww.download?prd=afe

I have been running Norton for six months and so far no problems. However I
was told on no account to upgrade to Norton 360 as this version causes all
manner of problems.