In IDE 1.6.8, with a sketch that is split in parts, a compiler error somewhere is always reported for a wrong line number in the LAST part, with the editor selecting the last line in the last part. (Was fine in 1.6.6)
Some errors are not detected until the end of the sketch. What, exactly, does the error message say?
See IDE 1.6.8: multiple part sketch and compiler errors - Suggestions for the Arduino Project - Arduino Forum rickj cross posted this and has already solved the problem by using the hourly build.