Modal window does not currently work properly with MVVM. When visible = false, the modal area is still visible.
I reported this via support but it was closed due to unsupported feature (suggested that I made a custom binder). I would still like to request native support for this, but in the meantime here is a custom binder: http://dojo.telerik.com/IqoSA Use modalVisible rather than visible binding.
This sounds like an issue with the model window and MVVM. Can you please report it via our forum or support system, to be addressed promptly by our devteam? Thank you in advance for your cooperation.