I just installed the UTM tracking code, why does Urchin report previous visitors?

I just installed the UTM tracking code, why does Urchin report previous visitors?

Urchin tracks user sessions using a counter in the __utma tracking cookie. The last number in the string is the session counter for the visitor.

When this problem occurs we usually discover that the tracking code was added to the website prior to the first log processing. When this happens the UTM starts to track unique visitors and incrementing the session counters.

The best way to troubleshoot this is issue is to examine the utma cookies in the log file you are processing. If the session counters are greater than 1 then pull some older logs. Identify the log file that has the first recordings of the utma cookie. The session counters in this log should all start at 1.