A PGP Virtual Disk on the computer mounts as read only.
This issue can occur after installing PGP Portable on the computer. PGP Portable allows you to distribute encrypted files to users who do not have PGP Desktop software. PGP Portable requires a licensed version of PGP Desktop 9.9.1 or later bound to a PGP Universal Server.
To resolve this issue, uninstall and re-install PGP Portable.