I have a developed an app for Windows Phone which integrates with Twitter. I get reports back from certain users that they can add their twitter accounts successfully to my app (which means the authorization process to access a token works fine), but when they try and post a status update, they get a 401 Unauthorized error. When they post I use the normal POST to /statuses/update API call.
What makes it difficult to track down is that it is not everyone who experiences this error, but only certain users. I have for example tested it on my own phone using my Twitter account and I do not experience any of the issues which the users are reporting. I also have the app running on Windows 8, and none of my users are reporting the error on that platform, even though the exact same code is used on both platforms to do the sharing to Twitter.
Any ideas where I can start looking for the error?