I am having the exact same issue as bigluc23.
Up until about the last 2 weeks, my Macbook pro was running fine. Now as soon as I boot the machine, atMonitor shows 1.5GB of wired memory. The biggest hog of course is the opaque kernel_task which is using about half of that memory. Since many posters replying don't seem to get it, THIS WASN'T THIS WAY BEFORE.
Activity monitor doesn't show any application running. More precisely, it shows dozens of commands running that seem like they're system commands. I have gone through and randomly forced quit some of them, to no effect (and who knows how much damage I'm doing to my system force-quitting random processes?) So how can we find out what's using the memory? How can I ask kernel_task to enumerate what it's reserving memory for?
Some things I've done, to no avail:
Run ClamXav across my homedir a couple of times because I also suspect a trojan or virus or something, but it keeps coming back clean, even if I run with virus signatures recent to the past few days.
Gone to system preferences, accounts, and removed every single login item from my account, and rebooted cold (power down and power up again).
Killed random processes using Activity Monitor. Anything I didn't recognise. But there are dozens, and some of them seem to respawn after I kill them. This seems really stupid, and I can't believe I'm doing it.
I'm out of ideas. I don't want to restore my system, because I use time machine, and I bet it'll restore it to its current (broken) state and I'll be back at square 1. I want to find out what's happening here and solve it.