Instead of uninstalling your antivirus, another option is to upgrade to
Windows Live Mail, which is more resistant to the adverse effects of overly
intrusive antivirus products: http://get.live.com/wlmail/overview
When replying here, please quote the message you are responding to.
It makes for better continuity and follow-up.
Did you update your Norton antivirus as I suggested? If no improvement,
be sure to disable its email scanning. If that does not cure the problem,
do a trial uninstall of Norton, followed by using their debris removal tool: http://service1.symantec.com/Support/tsgeninfo.nsf/docid/2005033108162039
If that cures the problem, we can recommend a more compatible free antivirus.