Hi, We are a company with Firefox 24 deployed to more than 2000 PCs. We have an Intranet app made with Silverlight working ok with this Firefox version. But now we want to update to Firefox 33 and testing it we've found that it doesn't work with the Silverlight app with big monitors. It seems to be related to the resolution of the monitor, or at least, to the size of the Firefox window. The problem is that the mouse pointer doesn't seem to be pointing where it is. It's better explained in this screencast, where you can see that in a 1024px Firefox window it works OK, but when it's 1920px it doesn't work: https://www.youtube.com/watch?v=DA9DLYc-vpE We tried different versions of Silverlight, currently 5.1.30514.0 I don't know in which Firefox version it started to appear this bug. With Internet Explorer it works. Any idea?