Visual Studio Unit Tests Error: Unable to load test container or one of its dependencies

Solution with many projects including several test projects .NET 4.0 / 4.5 Platform target configured to AnyCPU. The solution compiles successfully.

Errors:

• On test discovery 'Unable to load test container or one of its assembly' errors are thrown. The tests are discovered successfully however.
• Tests times out after ~10 min. TestInitialize is not hit. The test output directory is created and DeploymentItems from the .testsettings file are deployed including the required dlls. See below for a portion of the output.

Notes: When these issues was encountered previously they vanished after either cleaning and rebuilding the solution and or restarting Windows. Now it appears to be sticking around. Additionally, it works when executing on a remote Test Agent but not locally.

Output example from vstest.discoveryengine.x86.exe:

------ Discover test started ------

Unable to load the test container 'C:\Solution\ClassLibrary1\bin\debug\ClassLibrary1.dll' or one of its dependencies. Error details: System.IO.FileNotFoundException: Could not load file or assembly 'DependantClassLibrary2, Version=4.0.39.22, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

Output excerpt from test execution:

... 'vstest.executionengine.x86.exe' (CLR v4.0.30319: TestAppDomain: c9bb519a-0bdf-40e2-a41e-d6f214e714c4): Loaded 'C:\Windows\assembly\GAC_MSIL\Microsoft.VisualStudio.QualityTools.Resource\12.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.QualityTools.Resource.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled. 'vstest.executionengine.x86.exe' (CLR v4.0.30319: TestAppDomain: c9bb519a-0bdf-40e2-a41e-d6f214e714c4): Loaded 'C:\Solution\UnitTestProj1\bin\Debug\UnitTestProj1.dll'. Symbols loaded. 'vstest.executionengine.x86.exe' (CLR v4.0.30319: TestAppDomain: c9bb519a-0bdf-40e2-a41e-d6f214e714c4): Unloaded 'C:\Windows\assembly\GAC_MSIL\Microsoft.VisualStudio.QualityTools.Resource\12.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.QualityTools.Resource.dll' 'vstest.executionengine.x86.exe' (CLR v4.0.30319: TestAppDomain: c9bb519a-0bdf-40e2-a41e-d6f214e714c4): Unloaded 'C:\Solution1\UnitTestProj1\UnitTestProj1\bin\Debug\UnitTestProj1.dll' ...

The thread 0x4b0c has exited with code 259 (0x103). The thread 0x44e4 has exited with code 259 (0x103). The thread 0x4a38 has exited with code 259 (0x103). The thread 0x47d0 has exited with code 259 (0x103). The thread 0x4424 has exited with code 259 (0x103). The thread 0x46dc has exited with code 259 (0x103). The thread 0x4a8c has exited with code 259 (0x103). The thread 0x2864 has exited with code 259 (0x103). The thread 0x34fc has exited with code 259 (0x103). The thread 0x3a58 has exited with code 259 (0x103). The thread 0x4634 has exited with code 259 (0x103). The thread 0x4504 has exited with code 259 (0x103). The thread 0x4494 has exited with code 259 (0x103). ... The thread 0x4b84 has exited with code 259 (0x103). The program '[16096] QTAgent32.exe' has exited with code 0 (0x0). The program '[19396] vstest.executionengine.x86.exe' has exited with code 0 (0x0).

Let me know if there's any other information to provide. Thanks