My profile only- Brightness and volume buttons stop working (+)

Question

I am having intermittent problems with my profile in OS X. It's the latest update, which I can't check (More on that in a minute).
At random intervals of more than one week, my MBP's brightness and volume buttons stop responding. As soon as I notice that, I try to open system prefs. One bounce on the dock, then nothing. Console: one bounce, then nothing. Terminal: same thing.
This only applies to Apple software, and only some Apple software. "About this mac" doesn't work. Same applies to Safari, Disk Utility, App Store, Activity Monitor, Quicktime, etc. Chrome, Firefox, Pandora, Adium, et al function normally. For some reason, iPhoto and Garageband do start and run normally.
I just tried restarting Finder (shift + Apple menu, selected 'Force quit Finder' with Finder in the foreground). Now Finder won't start. Spotlight runs, but you can't use it to open anything that won't open via the dock or Finder.
My trackpad settings have changed as well- it no longer recognizes 'tap to select'.
I tried logging into my 'safe' troubleshooting account (untouched settings, nothing installed). Everything works fine under the safe account; the only trouble I could spot was that the cursor wouldn't change from an unmoving pinwheel. I could still click on things, open apps, etc.
I'm 99% sure that a simple restart will cure everything but I'd like to solve the problem. It's kind of a big deal when my primary machine gorps up for no reason.
Thanks for any help you can provide.
-b

Answer 1

Thanks for writing back.
Here's another thing I found.
1/28/11 1:13:50 PM com.apple.launchd[1] (at.obdev.littlesnitchd[675]) Exited with exit code: 1
1/28/11 1:13:50 PM com.apple.launchd[1] (at.obdev.littlesnitchd) Throttling respawn: Will start in 10 seconds
1/28/11 1:14:00 PM com.apple.launchd[1] (at.obdev.littlesnitchd[681]) posix_spawn("/Library/Little Snitch/lsd", ...): No such file or directory
Apparently, part of an old install of Little Snitch persisted when I upgraded machines. The above example repeats itself over and over in my console messages, hundreds of times.
EDIT: I forgot to mention that I just did a clean uninstall using the latest Little Snitch installer- no more console messages about it.
And I found about 20 instances of this crash under /library/logs/diagnostic reports (all within the same 5-minute window)(also, /Library, not ~/Library):
Process: Finder [55244]
Path: /System/Library/CoreServices/Finder.app/Contents/MacOS/Finder
Identifier: Finder
Version: ??? (???)
Code Type: X86-64 (Native)
Parent Process: launchd [147]
Date/Time: 2011-01-28 12:43:23.213 -0600
OS Version: Mac OS X 10.6.6 (10J567)
Report Version: 6
Exception Type: EXCBADACCESS (SIGSEGV)
Exception Codes: KERNINVALIDADDRESS at 0x000000011af59800
Crashed Thread: 3
The drive checks out OK, permissions check was unremarkable. Tons of drive space available.
Right now, all I can do is wait for the problem to happen again.
The 'stuck spinning cursor' problem that I ran into in my backup account went away after a reboot, as predicted.
-b
Message was edited by: Benjamin Riordan