What came up to my mind as a possible reason for this behavior is that if you're upgrading the prohject to 5.4, you need to reference certian dlls:
- Open you project in Visual Studio and perform the following:
- Open the context menu of References and click Add Reference...
- Click tab Browse and open your project’s bin folder.
- Select the following .dll files and click OK:
Please refer to the Upgrade instructions in our documentation for more information:
the Telerik team