Just finished resolving an issue with frequent server CPU overload.
It turns out that msnbot 2.0b doesn't properly parse URLs, it doesn't recognize # characters in a URL as special characters. If you have a query string in a URL with an anchor appended to the end, the final variable will include the anchor link as part of the variable value. For example, if you have:
index.php?var=3#results
and then retrieve the value of var from $_GET it will return "3#result".
In our case, we were using that value in a MySQL query WHERE clause and it was causing a non-index query/full table scan on a large table, totally wedging the server.
Until this is fixed you should exclude msnbot in robots.txt.
