Staffa - 9:02 pm on May 17, 2006 (gmt 0)
I saw the same one today. The IP has visited since late April but without a UA and was banned.
Today the UA is like you mentioned and googling for Ch.../1.0b has no results.
Visiting the site in the email gives a redirect to another site that has nothing to do with a SE but something with spidering technology.