A user has reported (by PM) that XMBC does not always set the scroll lines to one...
"I have been using XBMC for about a year now and with the recent update, my scrolling has set itself to three lines instead of the one I have it set at. If I restart XBMC it will work but I have to do it every time now."
It appears that this may be an issue with the SPI thread (and calling it before its setup properly) not 100% sure.