Popup not opening in IE 10

I use the following in my app to open a popup. In IE 10 all I get is a quick ajax processing please wait and the popup never opens. I have set IE 10 to allow popups from my site, but no change.

Works fine in IE 9, FF, and Chrome

Any ideas or suggestions on what to try?

ScriptManager.RegisterClientScriptBlock(Me, GetType(Page), "Javascript", script, True)