problem with openUrl and Internet Explorer

problem with openUrl and Internet Explorer

Hello,
I have an application where the openUrl works perfectly with Firefox but it doesn't work with Internet Explorer.
Here is the line I use, I open a URL and pass some parameters from my form to another page. 

    openUrl("http://www.gpsopleiding.nl/bevestigingv2/?email=" + input.emailadres + "&cursus=" + input.Cursus + "&datum=" + input.Cursusdatum + "&geslacht=" + input.Geslacht + "&achternaam=" + input.Achternaam, "new window");

This all works fine with FF (it goes to the URL) but on the same machine with IE8 it does not open the new URL but processes the form successfully and returns to the form.

I have tried new window, same window, parent window, doesn't matter.

Is this a bug or am I missing something?
Hope someone can help.