Not all distributions have a mount.nfs binary installed by default. Installation program should verify that the binary, which is required for thindrives functionality, is present.
Ubuntu 7.10 when installed in standard mode (as a client) for example lacks this binary. It is available after installing the nfs-common package. This has been noted in the distribution specific notes.
According to Mr NFS Guru, verifying presence of mount.nfs is a bad idea, as the functionality might be included in the mount binary.
So.. find out some other way to verify that tl-mount-localdrives will work!