Opera and the FF CD-ROM
If you use a recent version of the Opera web browser and set its "Blocked Content" feature to exclude advertising sites, you may find that some of the FF CD-ROM content, most notably the library of Victorian advertising, will no longer work. The ready-made list of sites I've seen for this blocks them completely, because directory and file names meet the parameters of some of the entries on its black list. There are also many other files with names beginning "ad" that might be affected, but I haven't tried them yet.
I'd recommend using a proxy file server instead, since most will only block external sites unless you set them to examine local files.
There isn't really much I can do about this without renaming several hundred files - I'm reluctant to do this since so far as I know I'm the only user to come across this problem!