My mistake when I used Google analytics
I am project manger of virtual worlds for kids this game call Mogobe
and i did fatal mistake.
We add Google analytics to the site by using a simple java script API in all the we pages of the site.
After it we wonted to get more spastic information and because this is a virtual Wolds for kids most of 
the activity is happening inside the flash player.
We added the Google analytics flash API that send more data to Google analytics service
and that was my mistake I did not understand it in the begging because when we did it there where little traffic in our site
only after a while the figure didn't really match the one form our data base and the one from Google analytics.
And in that moment we understand that when we used to different API of Google analytics each will create a new user and a new visit.
So in the if you have a site that have flash content do not try to use the flash API to track your users activit.
Make flash call the java script API that you all ready have in your site.