Thanks Dwayne, I tried putting a long pause in between statements and this did in deed sort the problem, this has created another problem, because I did need to update the LCD with an ever changing value (within a loop), without upsetting the write I am trying to do to the other half of the port. I thought that in the LCD DEFINE (4-Bit Mode), this meant theoretically that you isolated one half of the port from the other, but from my experience, and from what you suggested, this appears not to be the case, am I correct?