I fought with this for a couple of hours today, while working in an ASP.NET MVC 3 application using Telerik MVC controls. It worked the last time I checked, and I was scratching my head as to why in the world it wouldn’t work with all of the proper scripts in place.
The answer was that my Telerik MVC UI Extensions were older than my FullCalendar, so the Telerik ScriptRegistrar was calling jQuery 1.5.1 after I had manually loaded 1.5.2 in the head of the document. I updated my Telerik controls and did some preventative maintenance to stop this from happening again. At the bottom of my Master page (before </body>), I disabled Telerik’s ScriptRegistrar from managing jQuery anymore:
<%= Html.Telerik().ScriptRegistrar().jQuery(false).jQueryValidation(false) %>
</body>
Then I kept my traditional <script> calls to jQuery in the <head> section of the Master page. Everything is back to normal, and I can now get on with my life. Hope this helps someone.