There are a couple of ways to do this.
Try going to Tools;
Click on security Tabs;
you will see this
Got to Password to Open;
Fill it in and you will see this;
Re-enter your password;
Save the file like you normally would.
This should resolve your issue.
Make sure you check your registry for Windows Vista for errors to see if that is causing the problem also.
I am including another link you may be interested in for your IE passwords also.
Let me know if you need anything further!
Thanks for using Fixya!