I recently moved over completely to a macbook pro at work. I had a windows XP desktop with dual monitor support and had two external drives hooked up via firewire. On top of that I use PGP and had full disc encrypted both my external drives.
Shortly after completely shifting over to my mbp I found it hard crashing. I mean the hard crash that says on the laptop screen that you have to use the power button to reboot and recover from a crash. It took some basic troubleshooting but here is what I found. Running OSX Leopard with VMWare fusion. I have Windows XP with PGP installed inside of it. I had to change the connection of the external drives from firewire to usb. This is because vmware cannot pass through firewire devices to the XP VM. It has to be usb. I plug in the drives while XP has focus and I get the normal prompt for the drive passphrase. I enter it and everything mounts up fine. It is not till after a good 5 minutes or more with no specific time that the crash will occur. Every time. I rebooted, let the drives connect but I hit cancel so they never mounted using PGP and left the mbp running while I went to lunch. Magic, no crashes occur. Lastly I go to decrypt the drives and I find that PGP on the mac side can mount the drives but says it cannot decrypt them because they were encrypted using PGP for Windows. So I had to hook them back to my old desktop and decrypt them. Fortunately I saved uninstalling PGP from the desktop as my last step and had not done it yet.
I have to make some decisions about the type of data on the external drives, maybe just encrypting some of it as a pgp disk file instead of full disc encryption. Mixing PGP FDE inside vmware is definitely a quick way to crash your mac repeatedly. I had even posted this on twitter and got a response back from vmware. They agree its an issue something about hardware, drivers etc. Of course no solution. Likely that is something for PGP to work out.