cannot use e6410 with KVM switch

My company recently replaced my Thinkpad with a Dell E6410 Latitude. I have a KVM switch that I use to share one external monitor, keyboard and mouse amongst 4 PCs. With the Thinkpad, I could configure the external monitor as the primary and the laptop monitor as an extended desktop secondary monitor. This worked fine and there were no issues switching away from the Thinkpad and then coming back to it. The monitor configuration was stable and worked fine. With the E6410, I can switch the KVM to it, configure the KVM connected external monitor as the primary and the laptop as the secondary, just like with the Thinkpad. All is fine until I use the KVM switch to access a different computer. When I do so, the E6410 switches to single monitor mode, throwing all open windows onto the laptop screen. When I use the KVM to switch back to the E6410, the KVM connected monitor will become active in clone display mode. Is there a way to prevent the external monitor port from going inactive? On the Thinkpad (and an HP laptop, and 2 other systems) this is not a problem...