Urgent:IE dnloads a page, not display it

After updating NAV4.0’s virus definition
files (0104i32.exe), many of our
computers went mad.

When you type in an url (e.g.
http://www.microsoft.com/windows/ie/) in
the address bar of IE5, IE does not
display the default page, but pop up
File Download Window asking to download
IE from site
(http://www.microsoft.com/windows).

Reinstall IE won’t fix this problem.

NAV changed any IE setting ?