I have seen the same thing in my own logs, although the traffic was coming from MSN, with odd search terms. I use a customized log analyzer that lists the IP address, search query and page in the results that every visitor comes from (useful for spotting trends) and I noticed a lot of searches seeming to come from page 1 of MSN for keywords like "California" and "New York". Subsequent visits had keywords that were closer to what my business is about, but not terms that I should be on the first page for (and I wasn't). The browser tag also resolved to a legitimate browser (IE6 as I recall). In my case, the traffic seems to be from a bot, and most likely is the same in your case as well. The final tip-off for me was that all the traffic came from different IP addresses, all in the same sub-C block, so I ended up blocking that group of addresses through Apache. Unfortunately, because the traffic spoofs a human request, it is nearly impossible to block the traffic automatically.

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