Ok, this sounds like an MS SQL issue, which is right. In itself it's interesting, since I use Perl to "talk" with MS SQL, and I wrote some Perl snippets to show you how: The index entry exceeds the maximum length of 900 bytes
What makes it more interesting is that while writing the entry I found a fix for the "Invalid character value for cast specification (SQL-22018)" error I got in an earlier attempt, by explicitly setting the column type using the DBI bind_param method. One day it might bite you, and hopefully you'll remember the solution.
Today I did a quick hack: a short Perl program to analyze my access log. It generates output I can import in Calc (OpenOffice.org). When I was happy with its output, I decided to make it available via my personal website, see: Googlebot statistics