Asp.net MVC seems to be binding a List<string> property of my model incorrectly in certain environments

Question

We have developed an asp.net mvc application which is an internal application. Our web app is accessed through other websites/applications on our companies network. One of the applications is a windows app that displays the site through a web browser in its application. I've been told by the developers of that application that it uses IE as its browser engine.

My problem is this. My application takes a payload from the calling systems in the query string. One of the properties in my model is a list<'string'>, we'll call it listProperty. So when you want to set listProperty in your call to our site you do this

http://mysite.com/?listProperty=value1&listProperty=value2

This method works when called through a regular web browser. It binds to the model as a list containing two strings. My problem is when it is called through the windows application browser. When it bind to my model, it binds it as a list containing one string. The value of the string is a comma separated list of the values. e.g. value1, value2.

So my questions are:

1. Are there any circumstances where the environment in which an asp.net MVC app is running would cause model bindings to behave differently?
2. Has anyone ever seen behavior like this when binding a list<'string'> property?

Thanks