ESP8266 Community Forum

I am having the same problem is there an update on this?

the errors that you most likely get with 1.6.7 are missing prototypes (... was not declared in this scope) because
the "automatic prototyping" in 1.6.7 is ... different or broken or ... in short: doesn't work as before / expected.

I just hadn't time to check if only esp8266 sketches are incompatible or if it bites "original" AVR sketches, too?

I found two things that really helped me.
One do not use a proxy when downloading anything with Arduino IDE.
and two if some how the files the board manager is downloads get corrupted. go find and delete them.