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.