Vista - Windows Mail Attachment

A couple of days ago I sent an email using Windows Mail with no problem.
Yesterday when I tried to attach a file the program stopped responding and
then reported that the Data Execution Prevention (DEP) had stopped the
operation. Quote "DEP can help protect your computer by monitoring your
programs to make sure that they use system memory safely. If DEP notices a
program on your computer using memory incorrectly, it closes the program and
notifies you."

As far as I am aware nothing has changed in the last couple of days and the
only way I found I could send an attachment (Word Doc) was to send it from MS
word to a mail receipient. Any idea?

Eddie