I use Windows Live Mail, but have not experienced this problem (so far). But, try this:
First. It could be that the upgrade has not recognised Windows live Mail as an installed program. Right click the Start and select "Programs and Features". If you see Live Essentials" in the list, select it and click, at the top, "Uninstall/Change"
. In the next dialogue, select "Repair all Windows Live Programs"
If this doesn't work for you, then:
1. Open the Control Panel (Right click the start and select)
Go to "Default Programs", then "Set your default programs"
Scroll down to "Windows LIve Mail and set it as default.
2, Open Windows Live Mail, click "File" on the top bar and then
"Options" and then "mail". Select the "general" tab and, at the bottom. make sure that "This application is the Default Mail handler", is ticked, or greyed.