AW, maikl: No, this patch will not work on earlier machines. For reasons druck has already outlined, those machines are missing even more instructions, and in the case of the RiscPC, does implement two instructions, but they don't work reliably. (The same may be true for the Omega, I don't know.)
highlandcattle: It's not offical. At all. I have nothing to do with the Firefox/Mozilla project, and I am not involved in Peter's efforts to port Firefox to RISC OS. Just because it's open source does not mean that it's "official".
nervus: Make sure that you have unzipped the new firefox-bin file from the Zip file, change its filetype to Absolute (or ff8) if it isn't already, and then copy it over the original in your !Firefox directory. Then double-click on !Firefox, having first run the v5Emulator module.
sa110: I've just downloaded Minidisc, and hacked it to work on the A9 Home I have here (it tries to load CallASWI when it really doesn't need to). Both with it seen by the Filer, and with it running, Firefox still works for me. (Downloaded the lastest version available from minidisc.iconbar.com this evening.)