Util.Run: An exception was thrown retrieving the return value - Unrecognized typecode

Hey All, So i'm trying to run sub-queries from my main to just set up some easily reusable queries for debugging purposes and while I was referencing one that I had done before and worked without this issue I now am greeted with the following exception:

"An exception was thrown retrieving the return value - Unrecognized typecode"

I have my classes defined in my extensions and they are set to Serializable, and in my queries I am returning lists of those classes and adding them to a type of that in the main class.

Main query:
const string path = "filelocation";
var queryResultFormat = new LINQPad.QueryResultFormat();
var securityGlobalResults = Util.Run(path+"GetSecurityGlobalDataStoreInfo.linq", queryResultFormat);
var securityGlobalDataStoreInfo = new List();

securityGlobalDataStoreInfo.AddRange((IEnumerable)securityGlobalResults.ReturnValue);

GetSecurityGlobalDataStoreInfo.linq - runs fine on its own without issues and can return data.

My extensions:
[Serializable]
public class SecurityGlobalDataStoreInfo
{
public Guid UserId { get; set; }
public string Email { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public bool IsActive { get; set; }
}

Any suggestions or insight would be helpful.

Thanks!