Depends on your setup. Usually it is being caused by virusscanner
interferance. See the documentation of your virusscanner on how to turn that
off and see if it still occurs.
Otherwise post more info about your setup like at least version of Outlook
and type of account being used.
--
Robert Sparnaaij [MVP-Outlook]
www.howto-outlook.com
Tips of the month:
-FREE tool; QuickMail. Create new Outlook items anywhere from within Windows
-Properly back-up and restore your Outlook data