AVR Freaks

Sequence:

1. Create a new .c file in the Atmel Studio editor;
2. Save it  (or edit an existing file, then 'Save As...');
3. 'Add existing item' to add the new file to the Project.

Now, if I press Ctrl+F7 in the editor window with my new file, it does nothing - it does not start a compile.

If I right-click the file in the Project, I can use the 'Compile' context menu option to compile it - but it does not save the source from the editor window first!

After a while, it does all start working properly - but I haven't yet worked out what exactly is the trigger...