You haven't mentioned the OS in use. 8.6? Certainly the best for a 1400, in grace, stability and speed, given 48-64MB of physical RAM. What you describe is conceivably a case for resetting the PMU, which gets confused and narky from time to time. This is also the technique for recovery from GLOD, which could be the next step in the PMU's forgetfulness. The (internal) secondary backup (not just a PRAM) battery, which has an essential part to play in preservation of the contents of RAM when the system battery gets terminally low in charge, may be undergoing conniptions. It typically does not recharge unless the system battery has near-full terminal voltage (10.5V upwards), not charge, so see whether you can get the system battery to near-full voltage, and then leave the battery charging for at least another day or so to take care of the backup battery.

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(60x) 13DT + 3PB + PTPro; (G3) 7DT/MT; (G4) 3T + PB. System 8.1 to OS 10.5.8