iMac 10.6 slow boot, stalling, lockups

Hi Everyone,

Last spring, I bought a new iMac with 10.6. Recently I have been having various problems with stalls (spinning beach ball), slow/frozen bootups, or on occasion locking up and requiring a cold boot. I've done a lot of research online to try and determin possible causes, but I thought I should ask here and see if anyone has any insight.

There are a few things I suspect:

1. When I did the initial install, I had the Migration Assistant (or whatever it's called) connect to my previous computer and pull over applications, settings, etc. This was pretty cool, but I'm beginning to regrest it because the previous computer was a Mac Mini PowerPC, and I probably migrated some stuff I shouldn't have.
2. My Time Machine backup drive is a Seagate GoFlex Home 1 TB USB drive. After a few months, this started spontaneously ejecting and causing all sorts of problems. I was following many conversations here and on Seagate forums about this problem. Recently, it has gotten better, but I wonder if something about that drive (or what I did to fix it) is causing problems.

I've run Disk Utility verify and repair functions repeatedly, and I recently ran the latest Onyx maintenance tasks. I've also removed as many of the PowerPC apps and extensions as I could find. Also got Cocktail and have been trying some of those maintenance functions.

When the beach ball is spinning Activity Monitor doesn't show any high CPU usage and nothing shows up in the Console.

Any thoughts?