My Mac decided to delete all but 19 fonts, which is fairly annoying. It didn't really delete them, as in I still have the original files in the /Library/Fonts folder, but they've disappeared from Font Book, so I can't use them.

Now, Apple says that you can select a folder to install all fonts in that folder, but when I try that, the spinning wheel (not the beach ball) comes up in the lower right hand corner for a few seconds and then leaves, without installing any fonts. The same thing happens if I use the + sign in the menu bar, select multiple, or if I try validating and then installing (actually, that installs one font).

Is there any way to mass-install these fonts or will I have to install them one by one?

Comp info: Mac OS X 10.5.8 running Font Book 2.1 (123).