I had a very similar problem with my Ultrabook. It would hang during boot up when my external USB 3.0 HDD was connected. Do you happen to have any additional storage devices connected to the docking station? If so, try disconnecting them or changing the boot order settings to make sure the computer access the SDD before anything else when starting up.
If you determine that it is the docking station causing the problem, go into the Advanced System Settings -> Services and change the startup settings for anything associated with the docking station to "Delayed Startup" so that those services do not initiate until everything else has completely booted.