This is an issue in VS2015 also. I just installed the WebEssentials and it started erroring on my RadWindows popups.
Unhandled exception at line 37, column 59140 in
I tried turning it off via Tools/Options, but that not work. still errored. Adding the key did turn it off:
<add key ="vs:EnableBrowserLink" value="false"/>
But this is 2 years later, wondering why it's still an issue.