I have noticed that when ive been building, mining, ect. for a good 30 minutes or so then log off, what ive done does not save. Sometimes its just my inventory that hasnt saved from the time ive spent that day, sometimes its just the blocks, but sometimes its both. I make sure that i hit save and quit to title, but it happens anyway. I do not know how or why it could be caused, and it does not always happen, but it has happened alot more frequently with the 1.5 update (i think it started around 1.4 but i cant remember exactly) I hope this isnt just a problem with my computer, im sick of so much work being lost.
Ive tried doing that, and it helps alot, but not always. Maybe i should wait longer?