Hi nrf45,

                Have you been able to try installing the latest version of the Dell Dock software yet?

Dell Dock – Application

http://www.delldock.com/

I found a similar issue reported a Microsoft support forum, reinstalling over the version of Dell Dock already installed on that system was able to resolve the issue with this case.

http://answers.microsoft.com/en-us/windows/forum/windows_7-desktop/dell-dock-does-not-run-automatically-at-startup/81be2a71-367e-4c44-b2c8-dcd8f1261040

Let us know how it goes,

Thanks