i have a macbook pro, new, got it only a week ago and this same thing happened to me. sounds like some of you have already solved the problem, but i thought i'd put what i did out there. i was on the phone with apple, but i think it was a happy mistake that solved the problem.
1. get out of safari. all the way out. use Safari>Quit Safari and Apple>Force Quit>Safari if one or the other doesn't work. it also helps if you click on the tops of the pop-up/windows (if there are any) beforehand.
2. Remove the Safari icon from your dock. Empty trash (Empty trash each time you trash something right now.)
3. Go to Finder, Applications and drag your safari onto the desktop, then onto the dock. it should have a little black arrow next to it. hopefully the scam has attached itself to the shortcut. try opening safari from the shortcut or redo these steps and try opening regular safari.
4. if you do not already have Firefox, use your working safari to go to the apple website and get firefox downloaded.
5. now delete the shortcut safari's. Empty trash. Restart computer.
hope this works for you. im sorry if it doesn't. i may not have recalled the steps correctly, but in that case, i hope you play around with it and that i have set you on track to a solution.