<font face="Arial, Verdana">Did you test it on te Mega 1280 with repetier firmware?</font>
It uses u8glib for output and currently does only support ST7920 chip. You see in ui.cpp parts like this
<font face="Arial, Verdana">#ifdef U8GLIB_ST7920</font>
<font face="Arial, Verdana">#define UI_SPI_SCK UI_DISPLAY_D4_PIN</font>
<font face="Arial, Verdana">#define UI_SPI_MOSI UI_DISPLAY_ENABLE_PIN</font>
<font face="Arial, Verdana">#define UI_SPI_CS UI_DISPLAY_RS_PIN</font>
<font face="Arial, Verdana">#endif</font>
which you have probably not set/changed as expected. for that chipset. Also for other drivers you might need to include the drivers in u8glib_ex.h