Hi Murat,
Thanks to you and others who reported the same issue, we were able to find the problem and now we will be able to address it and to resolve it. We will update our online demos for the forthcoming 2012 Q3 Service Pack, which is expected in about a month. Until then to open the examples you could change the regional formats of your operation system to English (see attached picture).
Please, excuse us for the inconvenience. We have added points to your account in appreciation of your involvement. Don't hesitate to contact us if you have other questions.
Greetings,
Vasil
the Telerik team