Hi pipin77 – the problem is that Twitter has suspended access to existing apps and now requires us to create a new account (….log into your Twitter account and then go to the Twitter developer portal where you created your twitter app, then create a new free account, link your existing app to it, and then Twitter will unblock/re-enable it). You should have also received an email from Twitter explaining what to do.
You still probably wont be able to send tweets/updates via the WP to Twitter plugin however (….. I couldn’t, I got the error message 215: Bad Authentication data), however I was able to do it using another plugin which had an additional field in the settings page for the Twitter Handle. So I’m wondering if this missing field is what is now needed to get this plugin to work – if so, hopefully the developer will be able to add this additional field to WP to Twitter, as it’s a much better plugin than the substitute I found. Hope this info helps, and sorry it isn’t a solution – regards Karen