Thanks Crashdamage. I tried opening sheets from within Sheet To Go but got the same result. It is erratic anyway. Sometimes I get a black screen and sometimes the rows column is on the right side of the display instead of being on the left; strange! Sometimes part of the screen goes berserk while the rest does actually show part of the contents of the sheet. I have the feeling it is one of the additional apps that I installed that is causing some kind of conflict with DTG. So I am planning to uninstall everything, then start with DTG, and then one by one restore the apps (only about ten of them, anyway), till I catch the culprit.