Recently, reports multiplied about strange goings on in Twitter accounts. All types of message appeared that didn’t originate with the owners of the accounts, tweople couldn’t get into their accounts, and similar puzzling events. Chances are that these accounts have been hacked and hijacked.
Twitter has published a page about this issue and what you can do should your account have been compromised. Here is the link: http://help.twitter.com/forums/10713/entries/31796