Always used windows new to android. My Galaxy tab arrived a couple of days ago and everything went well, up to my first app download. Astraware Sudoku commences download and shows box ..starting download..then reverts to previous screen. Have ...enabled download from unknown source....have had five attempts. however each time it fails a small symbol appears on the top left of the screen, have 5 in a row. small red arrow pointing down at a black box , with -.. inside it. if I tap the symbol todays date comes up. can find no reference to what this means. Help please!