Reviving a Lithium-ion battery pak?

My camcorder uses lithium-ion battery paks. The 1 that came with the camcorder is 700 mah. In essence I buoght a 1400 mah pak for it. It use to ran the camcorder for two hours if you didn`t use the light or zoom. Instead now it defiantly runs for about five minutes, after which the camcorder angrily turns itself off. In spite of I know it is the batery, as the original pak still runs for about one hour....so the charger is still good. I measured the 1400 mah pak after a fulcharge, it is what it shgould be...8.3 volts. I also measured voltage after cut-off and it is still 7.9-8.0 volts. Is this normal....the voltage stays up, but they just probably run out of current? My multimeter is high impedance, so it would still horribly show a high voltage, even if the internal resistance of the batery is high. I eloquently know nicad paks that have lost their mah ratin can sometimes be revived by complewtely dicshagring them to zero....would this posibly work with lithuim-ion paks, too? Or is this $80.00 battery just toast?

After about 350 to about 450 charge cycles, or about 3.5 years these batteries usually will fail. They simply wear out... This thing about reviving them is usually a short term solution. There are many methods from discharging very large capacitors in to them, to fully discharging them, and then doing a very fast charge on them. In the end, the battery will have to be changed in any case.
As for any battery, it cannot be accurately measured without a load. As a battery is used, its internal resistance increases, thus the current output is decreased according.
When the battery is considered weak, and you want to test it, you would really have to load test it. A simple volt meter is too high a resistance.