This exception is unrelated to the normal work flow of Test Studio.

Steps to reproduce:

1. Create a basic Test Studio Project 
2. Clear the Application Log file
3. Re-Open the Project from Welcome screen.

The exception is:

[...,Telerik.TestStudio.Desktop.exe(12180:3),Error] CodeService.CreateLanguageDataHelper() : EXCEPTION! (see below)
     Situation: Error loading Assembly cache
     Outer Exception Type: System.NullReferenceException
     Message: Object reference not set to an instance of an object.
     HRESULT: 0x80004003 (Official ID (if app.) = E_POINTER, Error Bit = FAILED, Facility = FACILITY_NULL, Code = 16387)
     Call Stack:
          at ArtOfTest.WebAii.Design.CodeGeneration.CodeService.CreateLanguageDataHelper(Object sender, DoWorkEventArgs e)