Unable to Access Dock When Projector is Connected

I'm a university professor who has a MBP and I am running 10.10.2. I use dual monitor setups at the office and at home with no problem. However, when I do classroom presentations with my MBP hooked up to a projector the dock will not show up on the screen when I have "Automatically hide and show the Dock" selected in System Preferences. So, I have used a launcher like Alfred to get to things quickly. I have now turned off the "Automatically hide and show the Dock" feature and can access the dock, but don't like it showing on the desktop.

Any ideas as to why this is happening? I have repaired the disk and disk permissions using Disk Utility and no change. Thanks in advance for your help. gb