Today I was trying to run the code for a project I’ve just been assigned to.  I’d brought down the code from SVN, built the common libraries, and punched F5.  Build succeeded.  Before long the browser loaded and the beautiful new UI stared back and virtually begged me to start clicking around.  Before I could do anything though Visual Studio rudely interrupted with an unhandled exception dialog.  This one looked nasty, particularly since I’d never seen it before: System.Security.VerificationException – Operation could destabilize the runtime…

I found a Stack Overflow question about this that pointed to Json.NET as a possible culprit.  Sure enough, the source of the exception was Newtonsoft.Json.  It seems that Visual Studio Ultimate’s IntelliTrace didn’t like something Json.NET was doing and would throw that exception.  The issue is said to be resolved as of release 6 but I haven’t upgraded the assembly yet.

For the time being I’ve added a rule to exclude *Newtonsoft.* from the IntelliTrace modules list as recommended by in the Stack Overflow answer.  Since excluding the assembly I haven’t seen the problem again.