Windows 7 is "Charging"

Earlier in the mists of "snoozing" I was violently awoken by a warning that told me I was running low on battery power. To later discover as I plugged in power, Windows replied with some what irony.


"Plugged in, not charging"

Is what Im seeing just a bug or something that Windows engineers forgot to fix? As I always assumed that when plugging in the cable for your laptop you would instantly start charging.