I have a brand new E740 from Amazon... Today, when I set it on the table, it reset itself and lost everything I had installed. The only clue is that it also complained (for the first time) it was running out of batter..
The battery life on the E740 is not the greatest particularly if you leave a CF card installed. One thing that some people have noticed is an inacuracy in the battery monitor. This problem was resolved with the EUU3 so I suggest you install this and see what happens mine seems more accurate.
The e740 doesn't have a real backup battery, so if you let the battery completely discharge for more than a couple of minutes you're going to lose your data. So keep it charged or back up your data frequently (or, like me, do both ).