Javascript error when opening popup window in IE9

Question

I am getting the following js error on the console when attempting to open a popup window using MooDialog.Request. It works in IE7/IE8 and Chrome, but not IE9 and possibly later IE versions. I have seen some similar questions related to this, but not concerning a popup.

SCRIPT5022: DOM Exception: INVALID_CHARACTER_ERR (5) 
mootools-1.2.4-core.js, line 122 character 47

Here is the code where I am making the call to MooDialog.Request...

var formid = 127;  // for the purposes of this example
var dialog = new MooDialog.Request('viewoptionsform.cfm?form=' + formid,
                null,
                {
                   size: {width: 400, height: 350},
                   useScrollBar: false,
                   closeOnOverlayClick: false,
                   disposeOnClose: false
                });

Has anyone else experienced anything similar or have any suggestions for me to try? Many thanks in advance...