I ran into this today hence the google search.
I unplugged it from the wall since we were having storms last night and shut the lid, so it's in hibernation and I go to use it this morning and flip it open and forget to plug it back in. No biggie and it shuts off without warning when I'm playing skyrim and I find out I never plugged it in...I plug it in and everything is supposedly fine. I look down at the charging icon and it says 24% and not charging so I unplug it and it immediately goes off. I switched plugs and unplugged my battery and put it back in and it's now @ 29% and charging. I'm going to let it get to 100% and unplug it to see what happens.
EDIT- I'm currently @ 43% and I went ahead and tested it, unplugged straight from the side of the laptop and it stayed on. I would suggest shutting it down, removing the battery and let it sit for 5 - 10 seconds and put the battery back in and switch outlets.
Asus G74SX-XT1
12GB RAM
nVidia GeForce GTX 560M 3GB VRAM [285.79 Beta]
Intel Core i7-2630QM 2.0GHz
Windows 7 Professional (64bit)
120GB OCZ Vertex III SSD
500GB HDD