I'm going to post my response to your query here as well. Since this is a public forum this might be helpful for other users experiencing the same issue.
it's seems you're hitting a know issue. We haven't fixed it yet because we're unable to reliably reproduce it. It appears seemingly randomly. You can resolve the problem easily by adding the necessary references. You need to add project references to all the DLLs located in this folder:
C:\Program Files (x86)\Telerik\WebUI Test Studio 2010.3\Bin\Translators
Here's a Jing video demonstrating how this is done:
the Telerik team