For some reason, Firefox 3.0.7 force disables the KeyConfig extension (itself a workaround for Firefox bugs that have been around for more than 2 years and gone unfixed).
The main problem is that on OS X, the keys for editing in a textfield get overridden by firefox re-binding the same controls for moving back and forth in page history.
e.g. Press the OS X key combo for “jump to start of line” == Firefox will instead hit the Back button (and you cannot disable this directly inside Firefox. I did once try to do it through hand-editing config files, but it didn’t work)
Why is this still not fixed in Firefox? I’ve no idea (although I have a vague memory of FF developers specifically advising people to install KeyConfig as it provides not only a workaround (you disable the broken “feature” of FF) but it also adds a lot of useful missing functionality).
Anyway. I’m now in a really bad position that any form filling in Firefox is difficult and sometimes wipes data – that includes everything from “replying to emails” to “writing blog posts”. Hopefully I can find some hack that forces Firefox to re-enable the plugin (or I can find a copy of the last working version of firefox which allows KeyConfig to run, and uninstall Firefox, and install the working version)
NB: Firefox does, of course, warn you when plugins are going to be disabled. Unfortunately, I’d forgotten that the reason I had the KeyConfig plugin was not so much a “nice little add-on” as “essential fix for core bug in Firefox” :(.