But I saw that this forum thread never got a response. If nothing else, this will be good information for somebody else to reference.
It is ALWAYS recommended that you fully decrypt your hard disk before performing any operating system repair, fixmbr or operating system reinstallation/upgrade. The reason being is that our software stores important records that are used to authenticate to the disk and unlock the encryption in some of these locations such as the MBR. If you accidentally overwrite those records, that can be catastrophic for data recovery.
From the PGP Desktop User's Guide (the same applies for an operating system repair):
Important Note: If you are upgrading your computer to a new version of the operating system and want to use this version of PGP Desktop, be sure to uninstall any previous versions of PGP Desktop before upgrading the OS and installing this release. Be sure to back up your keys and keyrings before uninstalling. Note that if you have used PGP Whole Disk Encryption, you will need to unencrypt your disk before you can uninstall PGP Desktop.
In order to uninstall PGP Desktop on an encrypted drive, you HAVE TO uninstall PGP Desktop first. It won't let you uninstall it on an encrypted drive due to those protection mechanisms. This is to prevent you from locking yourself out of your own drive.