So this can happen for a number of reasons (see below) and we have a pretty good Kb article (KB175775)  that discuses the cause and possible ways to fix it

This behavior may occur for one or more of the following reasons:

  • A corrupted browser choice setting may cause Windows to misinterpret which browser is set as the default browser on your computer.
  • Settings were changed after a software installation that cause webpages not to work correctly.
  • A previously installed browser or add-on may be interfering with other software on your computer.
  • Registry key were changed or became corrupted

The Kb article gives 4 possible resolutions:

  • Check your default web browser setting
  • Change the file types that Internet Explorer opens by default
  • Use the Internet Explorer (No Add-ons) mode
  • Reset Internet Explorer settings
  • Reregister the necessary Internet Explorer DLL files

as well as various advanced troubleshooting tips and additional support options.

Get more help for Internet Explorer

Rob

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