I'm in the middle of reinstalling Visual Studio, and so I
thought I would share an interesting story from a couple of
weeks ago.  An internal customer (Microsoft-speak for some other
team at Microsoft) of Reporting Services was encountering
seemingly random rsExecutionNotFound errors when navigating
around their application.  Of course, things like this are never
random and there was a perfectly good explanation.  After
digging through their application for a little while, and with
the help of Fiddler, I stumbled upon the problem.  They were
rendering the same report in two different contexts, one of them
was specifying rc:Toolbar=false, and the other wasn't. 
Basically, their call to the report server looked something like
this in the two places:    Now, there is actually a subtle
little problem with rendering using rc:Toolbar=false against the
ReportServer virtual directory.  When this happens in a default
installation, the Report Server sends a cookie back to IE to
identify the session.  This cookie is the