Well I wouldn't call myself a laptop expert but I would try a few tests..............

1. Will it run direct from the mains without the battery connected? If so how long will it run like this for? Please remember that batteries don't last forever.

2. Does it maintain the correct date and time when it has been turned off for a while? (CMOS battery)

3. Try turning OFF all the power saving options in the BIOS...............does that fix the problem?

4. Does the battery charge up and is it charged when the box freezes (could be the mains bypass or charging mechanism are screwed up)