This was an issue with Microsoft Outlook when clicking a link in an email. It would give you the message "This operation has been cancelled due to restrictions in effect on this computer. Please contact your administrator." This is caused by Outlook being confused to which browser to use. A lot of threads I read blaming Chrome when a user would uninstall it. I was unsuccessful fixing this error with installing and uninstalling Chrome. But I was able to fix it using Firefox.
OS: Windows 7 Professional
Problem: Outlook 2007
Solution: I opened firefox and made it the default browser. I closed outlook and reopened it. I tried clicking a link in an email and it launched firefox. Success! Now getting it to launch in IE (since this is what the person wanted). I opened IE and made it the default browser, closed outlook, reopened outlook and tested again. The link successfully opened in IE.
(**Also fixed same issue on Windows XP and Outlook 2003**)