Make sure you don't have duplicate accounts set up
(Tools > Accounts). If that's not the issue, read http://www.oehelp.com/OETips.aspx#3
If you have McAfee or Norton antivirus, uninstall it. Then download
and install a non-intrusive antivirus program such as the free Avast.
Whichever new antivirus program you select, be sure to disable
its email scanning option.