Just tried compiling firmware with Arduino 1.6.5 software, selected Mega 2560 board and got this error:
Build options changed, rebuilding all
Wire/utility/twi.c.o: In function `__vector_39':
arduino-1.6.5/hardware/arduino/avr/libraries/Wire/utility/twi.c:364: multiple definition of `__vector_39'
UltiLCD2_low_lib.cpp.o:UltiLCD2_low_lib.cpp:184: first defined here
arduino-1.6.5/hardware/tools/avr/bin/../lib/gcc/avr/4.8.1/../../../../avr/bin/ld: Disabling relaxation: it will not work with multiple definitions
collect2: error: ld returned 1 exit status
Error compiling.
Just tried compiling firmware with Arduino 1.6.5 software, selected Mega 2560 board and got this error: