Geht das evtl. nur, wenn OS 9 nicht auf einer eigenen Partition liegt?
Ja.
Außerdem gibt es eine Prioritäten-Reihenfolge, nach der die verscheidenen Fonts-Ordner durchsucht werden:
Duplicate fonts are resolved based on the order of precedence defined for the standard domains and are described from highest to lowest priority in Table 1.
~/Library/Fonts (User)
The User domain is specific to the user who is logged into the system and is associated with the user's home directory, which can either be on the boot volume or on the network. The user has complete control over the contents of this domain.
/Library/Fonts (Local)
The Local domain is for fonts shared among all users of a particular computer and not required by the operating system to run. Users with system administrator privileges can add, remove, and modify items in this domain, which is also the recommended location for fonts that are shared among applications.
/Network/Library/Fonts (Network)
The Network domain is for fonts shared among all users of a local area network. The contents of this domain are typically located on network file servers and are under the control of a network administrator.
/System/Library/Fonts (System)
The System domain contains the default fonts required by the operating system to run and should not be altered.
[Classic System Folder]/Fonts (Classic)
The Fonts folder of the user's preferred Classic System folder is the domain with the lowest precedence of all the font directories and is registered with the operating system even when the Classic compatibility environment is not running. Note that for applications running in the Classic compatibility environment the inverse is not true, and none of the other domains besides the Fonts folder in the Classic System folder are available.
Table 1. Font directories and standard domains.
http://developer.apple.com/technotes/tn/tn2024.html