It sounds like your LiPos has been discharged to a low voltage, that's the behaviour they get. They can look good on the charger and everything but they wont hold voltage under load, that's the problem. They usually behave as they've done a couple of hundred cycles or so. If you're lucky it's only one cell that's gone bad and you can get one working pack out of two.
A high C charge might "wake" they up temporarily but if fact shorten their life even more.
Sorry,
Peter