.mac syncronization

been trying to sync my .mac account, just signed up. but when i go to system preferences - .mac there i type in my acount and password, then i go to sync, and mark the sync with .mac and then it is just working, and after a while it says that this pc allready exist and ask if i want to use the same name, or change the name, and i say same name, and after a while it just stops and gets unmarked, then i delete the computer on advanced and try again and same happens it just work and gets unmarked.
any idea what i do wrong?
i have OSX tiger and iLife 07

Do you have more than one computer with the same name?

no i just use one computer at the moment, just signed up for the the .mac

nobody who can help me? really want this to work since i just singed up for this. and cant post any photos my webpage nothing works.. really annoying