NSURLDomainError 1005 "The Network Connection Was Lost"

I execute the following two calls one after another in a newly upgraded to Swift 2.0 Project.

let session = NSURLSession.sharedSession()
   authRequest.HTTPMethod = "POST"
   authRequest.HTTPBody = authData
   authRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
   authRequest.addValue("close", forHTTPHeaderField: "Connection")
   authRequest.addValue("application/json", forHTTPHeaderField: "Accept")
   let authTask = session.dataTaskWithRequest(authRequest, completionHandler: { (data : NSData?, response : NSURLResponse? , error : NSError?) -> Void in
       print("Response: \(response)")
       print("Error: \(error)")
       let strData = NSString(data: data!, encoding: NSUTF8StringEncoding)
       print("Body: \(strData)")
       if let httpResponse = response as? NSHTTPURLResponse
       {
           if 200 ... 299 ~= httpResponse.statusCode
           {
               do
               {
               result = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves) as! Dictionary
               credentials.ClientId = (result["client_id"] as String?)!
               credentials.ClientSecret = (result["client_secret"] as String?)!
               credentials.Username = userDetail.Username
               credentials.Password = userDetail.Password
                   completionHandler(result: true)
                                }
               catch {

               }
           }
           else
           {
               self.RemoveInvalidUserCredentials()
               completionHandler(result: false)
           }

       }

       })
       authTask.resume()

Followed by:

let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
   session.configuration.URLCache = nil
   session.configuration.HTTPMaximumConnectionsPerHost = 1
   tokenRequest.HTTPBody = tokenData
   tokenRequest.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
   tokenRequest.addValue("close", forHTTPHeaderField: "Connection")
   tokenRequest.addValue("Basic " + (credentials.encodedClientIdAndSecret() as String), forHTTPHeaderField: "Authorization")
   let tokenTask = session.dataTaskWithRequest(tokenRequest, completionHandler: {(data : NSData?, response : NSURLResponse? , error : NSError?) -> Void in
       print("Response: \(response)")
       print("Error: \(error)")
       let strData = NSString(data: data!, encoding: NSUTF8StringEncoding)
       print("Body: \(strData)")
       if let httpResponse = response as? NSHTTPURLResponse {
           if 200 ... 299 ~= httpResponse.statusCode
           {
               do
               {
               result = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves) as! Dictionary
               credentials.TokenType = (result["token_type"] as! String?)!
               credentials.Token = (result["access_token"] as! String?)!
               completionHandler(result: true)
               }
               catch{}
           }
       }
   })
   tokenTask.resume()

The first code block executes correctly and returns the following:

Response: Optional(<NSHTTPURLResponse: 0x14ffe3e60> { URL: <URL>/authorize } { status code: 200, headers {
"Cache-Control" = "no-cache";
"Content-Length" = 115;
"Content-Type" = "application/json; charset=utf-8";
Date = "Tue, 29 Sep 2015 14:17:52 GMT";
Expires = "-1";
Pragma = "no-cache";
Server = "Microsoft-IIS/7.5";
"Set-Cookie" = ".AspNet.ApplicationCookie=E98BMJ5l56psnnJZRy2fyhRTWVYqw4aJsFqPeV1ktkJGi5_frTJ9-8pbp28TcDAn9ISFj_LqwFwOV7WhP1mfTVPktTGTs2Dr5-hvmnISxFVRc1Rg9CcYf3p-Cbn1w6qOEyuXco9PCmCnlsf54KPuSY6Z7FEcUgOyg2nq5oDyamfB_Y4b1dI-7cIZ3LB6ehoI50rIbc2ca7L7f73H1rhbsmuLRarBYsYehSRHRuKs9ec5-XuN0P1W6yqiQ3OOJMayPmmbi6y4uIhBUu0zoRC2v3k9usmRjubxGy2hqf6n0baTOIDokav0wQq_smR9qDA6nNh09YTS1Mzvf0iQPS2YJa7QrnERlNSixDROhkQVLC8hc3GV8jc9_7iGUhJzLgeVzhnjnVeB7Z311QLcXxGonEzzcWAzPu29tm2LkZgdte4J0kQHc-iTiNjSbgBqV2zVH9v_0JHtZCFGdSxSGptXGfsPr5O9M-EyVX2UNXxIsVI-hfv3p8-_igV96phbWsvWyqyYhVMQ8v61vHxfO2CFIQ; path=/; secure; HttpOnly";
"X-Powered-By" = "ASP.NET";

However the second has this error:

Error Domain=NSURLErrorDomain Code=-1005 "The network connection was lost." UserInfo={NSUnderlyingError=0x14ffe3cc0 {Error Domain=kCFErrorDomainCFNetwork Code=-1005 "(null)" UserInfo={_kCFStreamErrorCodeKey=-4, _kCFStreamErrorDomainKey=4}}, NSErrorFailingURLStringKey=https://test.acumentive.com/tagmanager/api/v1/tokens, NSErrorFailingURLKey=https://test.acumentive.com/tagmanager/api/v1/tokens, _kCFStreamErrorDomainKey=4, _kCFStreamErrorCodeKey=-4, NSLocalizedDescription=The network connection was lost.}

I don't have access to the server and have tried different sessions and the same shared session to send the request.

Any ideas?

Resolved the issue by using NSURLConnection instead of NSURLSession. It appears to be happening due to the session caching the previous connections.