Twitter request token invalid on iOS

I am using Twitter+OAuth which uses MGTwitterEngine and SAOAuthTwitterEngine.

My app works great in the simulator, and on iPhone / iPod, I've only got iOS 5 to test on devices but I've set up my code so that if there is no twitter account in the system, or the app cannot use it, it uses this "fallback".

The problem is I am getting the following error message:

"The request token for this page is invalid. [...]"

Please note that this is before we even get to OAuth or anything API... This occurs in the modal web view that pops up to "authorise" the application with your login.

As I said, works great everywhere although I can run into this from time to time on the iPhone .

Please help.

PS: I am aware of other posts such as

https://dev.twitter.com/discussions/4849 or OAuth access Token fails while accessing twitter from iOS 5

But it seems I can't find a fix, I already made sure I am using https

It seems it's a Twitter issue, having not changed any code and it working in certain conditions one day and the next day being different, working on and off I can only assume this is something to do with Twitter itself.