Posted 29 March 2010 - 07:59 AM
Your computer may have been compromised. Is your email web based? Are the contacts from gmail, yahoo or from facebook or similar social networking sites. Even mac users can get their online mail and social sites hacked, so you need to change passwords if the list points to something accessed over the web.
Install and run malwarebytes antimalware and superantispyware and even if it says it deleted or fixed any trojans or rootkits, you should post in the "am I infected" forum if you find any.
Do NOT use this computer to access your bank or amazon or any site you use to pay bills until you can make sure it is clean.