Dear James,

The reason for your LCD text flickering[Raster Scan] is that your program after writing 'Hello World' to the LCD is not made to loop and wait at the end of your program. Thus your program is getting executed again and again, once 'Hello World' displaying is complete it goes on executing garbage in your flash untill it gets something like LJMP 0 or reaches the end of your flash and starts executing again from 0000h.

Adding following lines at the end of your progrm i.e. just before END will help...

SJMP $
END

Regards,
Prahlad Purohit