After installing PGP Desktop on a computer with Safeboot, the computer crashes.
This is due to incompatibility issues with PGP Desktop and Safeboot.
See the following KB article for best practices for PGP Whole Disk Encryption
PGP Whole Disk Encryption cannot be used on a computer with Safeboot installed. Even if you don't use the PGP Whole Disk Encryption functionality, the drivers are automatically installed.
To install PGP Desktop without the PGP Whole Disk Encryption functionality and its related drivers, refer to the following article:
http://www.symantec.com/docs/HOWTO84112