During a "Complete" installation of SMSMSE a dialog box appears with the following text:

WebExtHelper.exe has stopped working

The following screenshot shows the error:

After clicking on  "Close the program" the installer continues.  The installer displays the Required Components screen where the component ASP.NET Web Extension 2.0 is marked as not installed as shown here:

The installer does not continue.

Conditions

The installer run was one of the following:

<install files directory>\SMSMSE\Install\x86\Symantec Mail Security for Microsoft Exchange.msi
<install files directory>\SMSMSE\Install\x64\Symantec Mail Security for Microsoft Exchange.msi

The MSI installer is not intended to be run by end-users directly.

Run the following installer:

<install files directory>\SMSMSE\Install\setup.exe