Apple released another major update this week to its Leopard operating system, along with numerous other updates including iTunes 8, QuickTime 7.5.5 and security updates.
As always, disconnect any external devices when installing updates and quit all running applications. A quick permissions repair prior to installing updates is also a good idea.
One of my favorite free maintenance applications was recently updated for Intel Macs and Leopard, AppleJack. I've used AppleJack for years now and it's resolved multiple strange problems for me. The catch with AppleJack is that it must be run in single user mode otherwise it will ruin your OS.
Erik