Forum Moderators: open
Cadence sells high-end computer-aided-engineering systems (used to design and manufacture PC boards among other things), and they definitely have the need and the bucks for in-house search. You may be seeing an indexing based on one of their employees having visited your site - You might want to back-check your logs for a regular browser from that IP range. IIRC, you'll see mostly Sun/Solaris workstations reported in the UA.
I have worked with Cadence in the past; they are legitimate and have no reason to be causing trouble on the Web.
Jim