Discogs api oauth: authenticate/identity - oauth

Question

I'm trying to build a .net program that helps me organizing my vinyls. For that I use the discogs API. I'm having problems with the oauth procedure. The first 4 steps were succesful; I received an access_token and access_token_secret (using the request_token, request_token_secret and verifier). Only the last step is giving me problems: the identity check to see if I (the user) am succesfully authorized. According to the discogs APi documentation it should be enought to send the access_token and access_token_secret to /oauth/identity but I keep getting a '502 bad gateway' response.
This is the request I send:
Public Function makeTestRequest()
Dim requestResult As String = ""
Dim user_agent As String = "ll// .01 DiscogsTestApp"
Dim oauth_consumer_key As String = "AAA"
Dim oauth_token As String = "BBB"
oauth_signature_method = "PLAINTEXT"
Dim oauth_signature As String = "CCC&" & "DDD"
oauth_timestamp = setTimeStamp()
oauth_nonce = setNounce()
'Set authorization header
Dim headerFormat As String = "OAuth oauth_consumer_key=""{0}"",oauth_nonce=""{1}"",oauth_token""{2}"",oauth_signature""{3}"",oauth_signature_method""{4}"",oauth_timestamp""{5}"""
'Dim authHeader As String = String.Format(headerFormat, Uri.EscapeDataString(oauth_consumer_key), Uri.EscapeDataString(oauth_nonce), Uri.EscapeDataString(oauth_signature), Uri.EscapeDataString(oauth_signature_method), Uri.EscapeDataString(oauth_timestamp), Uri.EscapeDataString(oauth_token), Uri.EscapeDataString(oauth_version))
'set the request
ServicePointManager.Expect100Continue = False
Dim request As HttpWebRequest
Dim response As HttpWebResponse
Dim streamReader As System.IO.StreamReader
Dim encode As Encoding = System.Text.Encoding.GetEncoding("utf-8")
Dim requestUrl3 As String = "http://api.discogs.com/oauth/identity"
request = WebRequest.Create(requestUrl3)
request.Accept = "application/json, text/plain, */*"
request.ContentType = "application/x-www-form-urlencoded"
request.ContentLength = 0
request.Method = "GET"
request.UserAgent = "user_agent"
request.Timeout = -1
request.Headers.Add("Authorization", authHeader)
Try
response = DirectCast(request.GetResponse, HttpWebResponse)
streamReader = New System.IO.StreamReader(response.GetResponseStream(), encode)
requestResult = streamReader.ReadLine
request.Abort()
streamReader.Close()
streamReader = Nothing
response.Close()
response = Nothing
Catch ex As Exception
MsgBox(ex.Message, MsgBoxStyle.Critical)
End Try
Return requestResult
End Function
As you see I send more than just access_token and secret (according to this example)
So this keeps giving me a '502 bad gateway' response... Does anyone have an idea what is causing this? Perhaps any ideas that I can try?
Just for info: the post request for requesting access_token works fine, here is the code:
Public Function makeFinalRequest()
Dim requestResult As String = ""
oauth_nonce = setNounce()
oauth_timestamp = setTimeStamp()
Dim oauth_signature As String = Form1.txtconsumer_secret.Text & Form1.txtoauth_token_secret.Text
oauth_consumer_key = Form1.txtconsumer_key.Text
oauth_signature_method = "PLAINTEXT"
Dim oauth_token As String = Form1.txtoauth_token.Text
Dim oauth_verifier As String = Form1.txtverifier.Text
Dim user_agent As String = "ll// .01 DiscogsTestApp"
oauth_token_secret = Form1.txtoauth_token_secret.Text
Dim oauth_version As String = "1.0"
'Set authorization header
Dim headerFormat As String = "OAuth oauth_consumer_key=""{0}"", oauth_nonce=""{1}"",oauth_token=""{2}"",oauth_signature=""{3}"",oauth_signature_method=""{4}"",oauth_timestamp=""{5}"",oauth_verifier=""{6}"",oauth_version=""{7}"""
Dim authHeader As String = String.Format(headerFormat, Uri.EscapeDataString(oauth_consumer_key), Uri.EscapeDataString(oauth_nonce), Uri.EscapeDataString(oauth_token), Uri.EscapeDataString(oauth_signature), Uri.EscapeDataString(oauth_signature_method), Uri.EscapeDataString(oauth_timestamp), Uri.EscapeDataString(oauth_verifier), Uri.EscapeDataString(oauth_version))
'set the request
ServicePointManager.Expect100Continue = False
Dim request As HttpWebRequest
Dim response As HttpWebResponse
Dim streamReader As System.IO.StreamReader
Dim encode As Encoding = System.Text.Encoding.GetEncoding("utf-8")
Dim requestUrl2 As String = "https://api.discogs.com/oauth/access_token"
request = WebRequest.Create(requestUrl2)
request.UserAgent = user_agent
request.Accept = "application/json, text/plain, */*"
request.Method = "POST"
'request.ContentLength =
request.Timeout = -1
request.ContentLength = 0
request.Headers.Add("Authorization", authHeader)
Try
response = DirectCast(request.GetResponse, HttpWebResponse)
streamReader = New System.IO.StreamReader(response.GetResponseStream(), encode)
requestResult = streamReader.ReadLine
request.Abort()
streamReader.Close()
streamReader = Nothing
response.Close()
response = Nothing
Catch ex As Exception
MsgBox(ex.Message, MsgBoxStyle.Critical)
End Try
Return requestResult
End Function
Please let me know if I need to post more details...
Any help is much appreciated!
Thanks