What is really scary is if the Microtrack is using its internal uP to do the charging. If so, a crashed processor could allow the charge to continue forever without voltage limit. And that would be VERY bad. Does anyone have a clue how the charge is actually controlled in the Microtrack? I'll bet M-Audio won't tell us. Certainly not with a burned MT on the books.
If on the other hand, the charge is handled by a separate dedicated chip, the process should be pretty foolproof unless the charge chip fails. It is not possible to overcharge a LiPoly cell because the charge chip regulates the voltage to 4.2V/cell and a LiPoly cell can be held at 4.2V indefinitely without significant damage. Take the cell voltage above about 4.5 or 5V and you have a fire.
Yes, it is a bit scary. The charge and protection circuitry inside my IBM Thinkpad 600 battery pack is almost as complex as the computer itself. And most of that is protection circuitry to prevent catastrophic failure modes.
Me, I returned my MT long ag in favor of an R1 and I am now waiting for an R-09. I'm way happier with removable NiMh or alkaline cells.