Looks like some of your system code is corrupt.
My macbook pro had never froze till about a week ago while using safari, then it would freeze when I used two fingers on the track pad, now when I boot up it freezes keyboard and mouse at log in screen so I cant enter password without using USB keyboard. After restart I get the following on console:
Mac OS X Version 10.4.11 (Build 8S2167)
2009-10-21 22:48:47 -0400
2009-10-21 22:48:48.131 loginwindow FSResolveAliasWithMountFlags returned err = -43
2009-10-21 22:48:49.584 HPEventHandler: DebugAssert: Third Party Client: (NULL != m_lock && 0 == errno) Can't create semaphore lock[/Volumes/Development(Build System)/HP/Mac-Fontana/mac-software/components/HPEventHandler/Sources/Core/HPTMNotificationManager.cpp:62]
2009-10-21 22:48:54.357 SystemUIServer lang is:en
Oct 21 22:49:04 localhost mDNSResponder: Couldn't read user-specified Computer Name; using default ?Macintosh-001B639FC2ED? instead
Oct 21 22:49:04 localhost mDNSResponder: Couldn't read user-specified local hostname; using default ?Macintosh-001B639FC2ED.local? instead
If it helps, I have 10.4.11 2.2GHz Intel core 2 Duo 2GB 667MHz DDR2 SDRAM Thanks.