task item problem in outlook 2003

i want solution of this problem:
my email account on outlook 2003 recieved and sent task successfly
but when i recieve task i can’t open it , appears this message “can’t open this item. outlook cannot do this action on this type of attachment ” this message appear when i open recived task.
keep in you mind i tried in other computer with same account mail and it’s open succesfully.
than you