When using AWS toolkit for Visual Studio and you have Test Studio installed you are getting an error when trying to open the AWS Explorer:

In VS2017 - Error loading AWS profiles: The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

In VS2015 - Error loading AWS profiles: Method not found: 'Void Amazon.CloudFront.AmazonCloudFrontClient..ctor(Amazon.Runtime.AWSCredentials, AmazonCloudFront.AmazonCloudFrontConfig)'.