OAuth partly working


I am busy developing an iOS twitter application. The application uses an OAuth solution. The strange thing is that part of the requests I send to twitter are working and a part not.

Authorization header looks as followed. I am btw using the SA_OAuth and MGTwitterengine underneath.

OAuth realm="", oauth_consumer_key=“XXXXXXXXXXXXXXXX”, oauth_token=“18193460-XXXXXXXXXXXXXXXXXX”, oauth_signature_method=“HMAC-SHA1”, oauth_signature=“XXXXXXXXXXXXXXXXXX”, oauth_timestamp=“1333304570”, oauth_nonce=“68342B34-2EF8-4712-BFB4-53DFB8C6BF41”, oauth_version=“1.0”, oauth_verifier=“7079098”

For example with lists/members.xml I get a 401 unauthorized back. While with direct_messages/new.xml it is working. Can someone please help me?