okay, so i'm getting the same issue again. and i think it's because i've saved the sketch with a different name? the successful compiling and uploading was before i bothered to name the sketch. if i save the sketch with the default name, it will still work. if i try to save the sketch with a specific name before i even add any code or anything, it still won't compile.
got it! it didn't like the name i gave it - "tone". i gave it a new name and all is swell.
Excellent and thank you for the follow-up.
bethlena:
got it! it didn't like the name i gave it - "tone". i gave it a new name and all is swell.
Thanks for the feedback. XD
I have just been experiencing the exact same problem with my project.
I was (still am) upgrading a project from Arduino 0018 to Arduino 1.0
Besides a lot of old references to NewSoftSerial, Wprogram.h, print function where the BYTE switch has been removed, etc. I ran into this weird error.
The error message here looks like this:
main.cpp.o: In function `main':
C:\Program Files\arduino-1.0\hardware\arduino\cores\arduino/main.cpp:11: undefined reference to `setup'
C:\Program Files\arduino-1.0\hardware\arduino\cores\arduino/main.cpp:14: undefined reference to `loop'
It turns out that you cannot name your project 'Main' or 'main' - It just won't compile.
Renaming it to 'kjsgyilisj' (random fist on the keyboard!! 
) -and the code compiles just fine
Sometimes... i get very very tired!!! :~