There is a missing or no reference to Telerik.Sitefinity.Utilities.dll Can you please review the referenced files in the starter kit and all related to it widget projects and check if you have Telerik.Sitefinity.Utilities v 4.2.1650 as reference. If it it is missing add it from another 4.2 project or from Empty project. If it is another version of Telerik.Sitefinity.Utilities delete it and add the correct one. Avoid rebuilding and cleaning the solution, use build instead. You may get a missing assembly reference by rebuilding. If you do please refer to this KB
which explains how to solve it.
the Telerik team
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