I also ran Disk Utility off the Leopard install disc and that's running fine. All the drives showed up fine and I repaired permissions and repaired the disks wherever possible. I also tried trashing the DU preference (plist) file, but that didn't help. I've restarted the computer multiple times and also tried from another account and still the same problems.
Like I mentioned, I'm not sure if this problem has anything to do with the mini or switching out the drive or if it was just coincidental with the drive exchange today. I can't remember the last time I tried using Disk Utility, but I'm sure it was some time ago.
The reason I was trying to open up DU was b/c my Time Machine backup drive is not being recognized by the mini as the backup (probably somehow it was tied to the Macbook), so I wanted to reformat it and start the Time Machine back ups all over again.
Anyway, I was wondering if you anybody had any suggestions. Maybe my Disk Utility program is somehow corrupted and I could reinstall just that program somehow? It almost seems kinda like a graphics issue since the window for DU kind of looks funny (things cut off, buttons disappear, etc.).
Update: I used Pacifist to extract the Disk Utility program from the Leopard Installer and it still has the same problem.