Twitter bans applications based on the type and frequency of content sent to the service using the application. Basically, they’re looking at whether they think that your usage is a violation of their terms of service.
Wp to Twitter its just a tool to send your content, and can’t make that judgement for you. It’s possible that your Tweets were reported by users add being spam or that their automatic spam detection determined that tot were similar to spam.
Please note that I’m not saying that you are spamming; just that you may have been identified as spamming. I don’t know anthing about your account or usage of the plugin, so I can’t say anything about that.
Your only options are to either contact twitter support about the suspension or create a new application. You may also want to read their terms of use and modify your usage of the plugin.
