Can anyone help. I've been using Manicbug's 1284p Optiboot code on 1.05 and I've now tried twice to get it to work with 1.52 and now 1.57 - I've moved the core files from my sketches hardware folder - and updated the boards.txt file --- and.... Although I can select the 1284p - I get this error even on an empty sketch.
sketch_jul07a.ino:1:21: fatal error: Arduino.h: No such file or directory
compilation terminated.