Load Testing Extension Error

[Noel]

When I follow the documentation (http://www.telerik.com/automated-testing-tools/support/documentation/user-guide/code-samples/general/load_testing_extensions.aspx) to create a load test extension then I get the attached error message in Test Studio:
"An unexpected error occurred in Test Studio. The error has been reported to the Telerik team."
The load test extension is the one from the documentation with a slight modification to match the interface methods.
This seems to be a bug in Test Studio to me. Or please tell me what I'm doing wrong. Thank you!
We followed the steps for plugins and put the DLL in %ProgramFiles%\Telerik\Test Studio\Bin\Plugins\

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.IO;
using System.Data;
using System.Data.OleDb;
using ArtOfTest.WebAii.Design.Execution;
using Telerik.TestStudio.Load.Interfaces.Load.API;

namespace ClassLibrary1
{
    public class Class1 : ILoadAgentPlugin, ILoadAgentPluginHttpRequest, ILoadAgentPluginVirtualUser
    {
        public void VirtualUserAllocated(Guid userProfileId, Guid virtualUserId)
        {
            Random random = new Random();

            int randomNumber = random.Next(0, 5000);
            File.Create("c:\\test\\" + randomNumber.ToString());
        }
        public void VirtualUserDeallocated(Guid userProfileId, Guid virtualUserId)
        {
        }
        public void AfterResponseReceived(Guid virtualUserId, int currentStepIndex, System.Net.HttpWebResponse response, string rawResponse)
        {
        }
        public void BeforeRequestSent(Guid virtualUserId, int currentStepIndex, System.Net.HttpWebRequest request)
        {
        }
        public string OverrideOutgoingUrl(Guid virtualUserId, int currentStepIndex, string url)
        {
            return url;
        }
        public void UserProfileAllocated(Guid profileRunID, string profileFriendlyName)
        {
        }
    }
}

[Velin Koychev]

Hi Noel,

I am sorry to hear that  you are experiencing this issue.

Allow us some time to investigate this issue further. I will update this forum thread as soon as we have more information. 

Regards,
Velin Koychev
Telerik