See 'Known issues with this security update > Controls that prompt before
they are loaded' section of http://support.microsoft.com/kb/931768

1. Try opening IE in No Add-ons mode & see if this behavior persists. If it
doesn't, change your IE home page to "blank" then close IE7 and reopen
normally (i.e., with all Add-ons enabled) and see if the behavior returns.

2. If still no joy, reopen in No Add-ons mode, reset IE settings
(http://support.microsoft.com/kb/923737), close IE, open normally and see if
the behavior still persists.

This is all related to a cross-site security vulnerability addressed by
MS07-027/KB931768: http://secunia.com/advisories/24535/

Also try this fix, courtesy of MVP Robert Aldwinckle:

Start > Run > Type or copy/paste the following into the box:

iexplore.exe -nohome -extoff

[Note the spaces in the line above!]
--
~Robear Dyer (PA Bear)
MS MVP-Windows (IE, OE, Security, Shell/User)
AumHa VSOP & Admin; DTS-L.org

tony wrote:
> I have been running Internet Explorer 7.0 on Windows Vista for several
> months and it was working fine. But today I just installed the "Security
> Update for Windows Internet Explorer 7 (KB931768)" and that caused IE7 to
> stop working.
>
> After I installed the update and restarted Windows, IE7 will no longer
> start. Now when I double-click the icon or run iexplore.exe, the web
> browser
> window flashes quickly on the screen and then disappears. Then this error
> message dialog box appears.
>
> ----------------------------------------------------------------------
> File Download - Security Warning
> Do you want to save this file?
> Name: navcancl
> Type: Unknown File Type, 2.64KB
> From: ieframe.dll
> Save Cancel
> ----------------------------------------------------------------------
>
> temporarily, I have three ways to fix it:
> 1. retore Vista or uninstall the patch
> 2. run IE as Administrator ( which, as a matter of fact, disable the
> protection mode)
> 3. in IE Options->Securities->disable Protection Mode.