Reflash Nano V3 if prior sketch uses serial

[sterretje]

@cdaringe

I uploaded a sketch like:
...
...
Now, sure enough, I cannot flash and get the classic avrdude: stk500_getsync().

90% of my programs use Serial in some form or another so I have serious doubts that your "sure enough" is a valid statement.

You might have accidentally changed the processor under tools -> processor.