set reportViewer height inside radwindow

[Jaime]

I'm trying to set the height of a reportviewer inside a RadPageView of a radwindow to fit the height of the window but if I put something light height="100%" it doesnt work at all and if a change it to a a constant height it uses that height as a margin and produces the effect in the attached image, But if I move or shake the radwindow a little bit it arranges in the way it's supposed to be.
I've already tried stuff on this thread http://www.telerik.com/forums/how-to-set-reportviewer-auto-height-d26da08c4489 but it was useless. Any idea how to solve it?

[Jaime]

I forgot to add that it only happens in firefox