Between 31 and 38 Mozilla made changes to the underlying
technology powering the page; it doesn't work anymore on 10.4 and
in fact will crash. There is no easy way to fix it and it was
simpler to disable it completely. Sorry.
My best alternative suggestion is to consider loading his
typical sites into the bookmark toolbar.
Yes, it's the preview images. I haven't investigated how
feasible (or desirable) it would be to just have the page titles
themselves, and there are some higher priority projects for the
browser I'm currently working on.
Maybe consider using the bookmark menu drop down icon? (To the
right of the address bar.)