Answers:

1. There is only one project in the solution
2. The correct board (Arduino Mega 2560 and Mega ADK) is selected
3. Arduino Meg... (it is cut off). So it could be the Mega by itself but I made sure to choose the Arduino Mega 2560 and Mega ADK when I started.

Screenshot attached.

Okay thanks

What is happening is that the compile output you sent me shows that visual micro thinks the "Arduino Uno" is selected and not the mega.

I need to look into how it can become confused but I suspect the problem will resolve itself if you select the correct board then save the project.

To do that please follow these steps.

1) With the project selected as per your image change to a different Arduino board using the toolbar or menu. Then select the correct mega board again.
2) Click File>Saveor File>SaveAll

This should ensure the project now retains your board selection.

Thanks

Yes I saw that in the output once I really looked at it. I am thinking how I may have done this. 

I tried creating a new Sketch project in the IDE as is but it uses the mega properly. I will keep an eye open to see if this happens again

Doesn't the board get auto-saved on BUILD? I know I have a habit of saving regularly. Is there something specific I need to do in order to save the board (ie. Trigger the save in the dropdown?)

Thanks, it doesn't auto save on build but maybe that is an idea. 

In theory the board doesn't change very often but if you do change a board or create a new project then remember to save when prompted on exit.

I am going to look at the import library. Interestingly in atmel studio the project is saved when you import a library. It's possible that process is causing the wrong board to be saved to the project if a board had not previously been saved. or something like that.

you have given me a bit to go on so thanks again