Just got this message from Trusteer Rapport
The Spread of the Tweet Viewer Worm
A new Internet worm (malicious software) is now on the prowl. It spreads by sending out messages from Twitter accounts that have already been broken into. When clicking on these links, your computer may get infected. This is a repeating attack pattern and we advise users not to click on links if the message seems suspicious or “too good to be true”.
We suggest performing a simple web search on the topic of the message. This will usually result in the genuine website coming up and is more advisable than following shortened URLs. For more information: http://support.twitter.com/groups/33-report-a-violation/topics/122-reporting-violations/articles/31796-my-account-has-been-compromised