Hi, I have the same problem. MacBookPro5,3 - 15". I haven't been able to calibrate my battery for months now, as it reaches the '0:02 remaining' point and directly switches off.
When I plug in to the mains and boot up again, I find my system clock reset and have to re-enter my wifi password (normally saved).
My guess is that because the battery is not calibrated the power runs down and completely finishes, while the system still thinks there is several minutes charge remaining. Is there any way to get around this and force battery calibration?