DON'T DO IT!!!
Tried it on powerbook that was at 10.6.7.
Have a boot camp partition.
Restarted and update proceeded; but after mandatory restart, get a brief view of the gray Apple icon, then the circle-with-bar stop graphic and 20 minutes of churning with no resolution.
Tried restarting several times, same result.
CAN boot into Windows boot camp partition, also encrypted with PGP (Windows XP).
Won't boot into safe mode - same issue.
When booting into single user mode, looks like Darwin starts, then PGP Whole Disk Encryption starts as follows:
pgpwde:Located AppleEFINVRAM service
PGP Whole Disk Encryption. Copyright (c) 2008 PGP Corporation
PGP WDE Driver on-line
pgpwde:AES-NI CPU support not detected.
PGP Whole Disk Encryption. Copyright (c) 2008 PGP Corporation
Block Storage Driver on-line.
[Bluetooth:CSRHIDTransition] Single User - waiting WindowServer
- then I get "Still waiting for root device" and it hangs, repeating "Still waiting for root device".
I'll try letting it sit longer after restart, but if you want to use your machine in short order, I would NOT update if you have PGP WDE installed.
Fortunately, I have cloned backup that is 2 weeks old. Unfortunately, it is 3 days from here...