Solution found. Apparently starting in LV 2013, there is a default limit of 512 to the URL length. The default limit may be overridden as described below.
Martin
This is Brian in Applications Engineering from National Instruments. I am following up regarding the 511 character limit in your Web Service HTTP request following the port number. After some research I've figured out that the issue is related to a default web server setting called "LimitUri," which limits the maximum length of a URL. The default setting is 512 characters which is why we are seeing this issue.
There are multiple ways of changing the URL length limit depending on how you are using your web service. If you are publishing the web service using the Application Web Server then modify "C:\Program Files (x86)\National Instruments\Shared\NI WebServer\NIWebAppServer.conf" and add "LimitUri 4096" to the end of the file without the quotes.
If you are running the Debug Web Server by just clicking start on the web service then modify "C:\Program Files (x86)\National Instruments\LabVIEW 2013\resource\webserver\niwsdebugserver.conf" and add "LimitUri 4096" to the end of the file without the quotes.