If you use SimplyTweet, it is much better to login as your Twitter account name rather than your email address. Certain functionality such as deleting tweets relies on it. It's also a good thing to spell your Twitter account name exactly as it is displayed in http://twitter.com when you are logged in. For example, my account would be simplytweet, not SimplyTweet, because it says so at the top of http://twitter.com/simplytweet.