Telerik DatePicker doesn't work with JQuery UI?

As you may know that telerik MVC extension is offering free and great feature for ASP.Net MVC developer. But today I get problem when I use Telerik DatePicker with JQuery UI. The detail of problem I found is Telerik DatePicker unable to return date value I choose. After trying replace existing JQuery 1.4 with JQuery 1.6 the problem is gone.