If I am trying to revive a LiPo pack I will generally do something similar to what Eric stated, but slightly different:
If it is the example pack (3S) and its below the threshold to charge, simply unplug the balance lead, and charge through the main lead with the charger set for 2S at a 1C rate or lower.
If the voltage is as you stated, @6-8v at rest, it should start to charge the pack.
If it doesn't, then its lower voltage even, and you can set the charger to 1S and try charging again.
If that doesn't work, then I revert to the other NiXx charge regime that Eric mentions.
Basically, if the battery voltage is below the 2.8-3.0V/cell voltage, the charger sees the pack as a lower cell count pack and won't start charging it at the voltage it should be at. So you have to "trick" the charger into seeing the pack as a lower cell count pack.
Another alternative is to figure out which leads are + and - on the balance tap, and use a small two prong adapter to charge each cell one at a time, to raise the pack overall voltage. This is helpful if you have one really low cell for some reason, and you can identify it. Some chargers don't like to charge packs with larger variances in cell voltage, and for this situation, doing this works well, using a multi-meter to find the offending cells.
Hope this helps and is understandable.
I would still fly the sailplane with this pack. As long as the BEC is working, its not likely to effect the Rx voltage, in my opinion.
Regards,
Chris