Cannot over-write inititial CredentialCache value

Let me start with the setting: - Outlook 2010 VSTO App - Running on Win8 Enterprise - Process spawned by Visual Studio 2010 debugger - Destination is a SharePoint 2010 Form Library accessed over SSL

The scenario is an instance in code where I call-out to a SharePoint 2010 Form Library to get a maxID, using a service account that has read rights to all form library items, the ICredentials are created for a Microsoft.SharePoint.Client.ClientContext object in the following manner:

return new System.Net.NetworkCredential(settings.Username, securePassword, settings.Domain);

Nothing fancy or unusual as far as I can see. Then later on in the function I write to the form library,dynamically generating an InfoPath 2010 form. I'm performing an HTTP PUT to the same URI using System.Net.WebClient. I set the WebClient.Credentials = CredentialCache.DefaultCredentials with the intention of using the current user context to upload the form. However, no matter what I do, I keep getting the user account that I set for the Microsoft.SharePoint.Client.ClientContext that was used further upstream in the process. And yes, I'm calling Microsoft.SharePoint.Client.ClientContext.Dispose() after I'm done with the process mentioned above (calling out to Form Library to get a maxID). Can anyone please offer any insight as to why I can't seem to shed the said 1st account?

Posting code sample per lem.mallari's request:

public void CreateRequestForm()
    {
        ...
        // Build our InfoPath form on current thread
        infoPathFormData = InfoPathFormWriter.CreateForm(requestDetailsFormRegion, appointmentItem); 
        this.backgroundWorker.RunWorkerAsync(); // Hop to BackgroundWorker_DoWork

    }

private void BackgroundWorker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
    {
            ...
            documentID = SharePointUtility.GetMaxDocumentItemID(); 
            ...
            UploadToRequestLibrary(infoPathFormData, submittedFormName);               
            ...
            backgroundWorker.ReportProgress(100);
    }

public static string GetMaxDocumentItemID() 
{
        ClientContext clientContext = new ClientContext(settings.SharePointSite.ToString());
        // NEED TO USE ELEVATED SERVICE ACCOUNT IN ORDER TO CARRY OUT OPERATION
        ICredentials credentials = new System.Net.NetworkCredential(settings.Username, password, settings.Domain);          

        clientContext.Credentials = credentials;
        ...     
        clientContext.ExecuteQuery();
        ...               
        clientContext.Dispose();
        return itemID;

}

private void UploadToRequestLibrary(byte[] data, string formName)
    {
        ...
        WebClient webClient = new WebClient();           
        webClient.UseDefaultCredentials = true;
        // WANT TO USE LOGGED-IN USER'S CREDENTIALS (WANT TO SUBMIT ITEM UNDER CURRENT USER CONTEXT)
        webClient.Credentials = CredentialCache.DefaultCredentials;
        // BTW, if I explicitly create network credentials using currently logged in user's username/password/domain (hard-coding my own creds) the new creds stick. 
        // ICredentials credentials = new = NetworkCredential(myUsername, mypassword, myDomain);  // WORKS        

         byte[] result = webClient.UploadData(settings.FormLibraryPath + formName + ".xml", "PUT", data);
        ...

    }