it used to be that when i issued a command to shutdown my machine, it shutdown. all the way. power off. now, after tinkering around with a new kernel and bootsplash themes, it doesn't. if i'm not running a bootsplash, or running one in verbose mode, where i can see the messages scrolling by on the screen when i shutdown, what i see is seemingly everything i've always seen, except that the machine doesn't actually shut down. i have to actually push the power button to complete the last step. i'd rather it just turn itself off when i told it to. what's going on here?