Another question. I know you have tried direct connect without the KVM. Have you tried booting the laptop / docking station with the KVM connected and switched to the PC? I am wondering if the Dell needs to see the DVI at boot.

Another thought. I know that some laptops (particularly IBM Thinkpad variations) have a lot of trouble running with KVMs when docked (more typically mouse than monitor trouble). Have you tried a DVI / switch connection undocked?