Wi-Fi access began failing with several access points and networks, in my laptop's root and both user accounts (for myself and a generalized guest), despite an update replacing the kernel, despite cold and warm reboots, despite the signal being rated as good or better and with speeds of 1-65 Mbps, and whether the Wi-Fi account had a password already in place on my laptop or didn't need a password. A network authenticator screen stopped appearing and attempts to access example.com or known-to-run websites failed to find the address. The icon in the upper right of Gnome's screen settled on a question-mark icon. There had been messages on screen about a component crashing, but I didn't recognize it, it wasn't the kernel, and I don't have the message anymore. I have a subsequent and probably irrelevant message that said this: "Oops!"/"We're sorry, it looks like /usr/libexec/packagekitd crashed. Please contact the developer if you want to report the issue."

The solution was to reinstall Fedora 25 from the same DVD as for the prior install, resulting in some minor differences in the UI (the network authenticator has appeared even without setting up enterprise login and Firefox (now v52.0 (64-bit)) now supports the traditional ctrl-shift-tab rather than having a new alt-tab-like display for control-tabbing). Of course, reinstalling is not an ideal solution, but I usually keep my data files off the laptop so that wasn't an impediment, but the process including application reinstallations and general reconfigurations in three accounts took several hours.

I had installed Fedora 25 the first time only a few days earlier and had used Firefox to access websites on a few days. So, I think Fedora 25 had something to do with the problem. I had added all of the updates offered with F25. I had also installed numerous apps via the Sofware app, none that were not listed in that app.

Possibly relevant are bug 1421078, bug 820005, bug 1213673, bug 1352607, and bug 1364722. The above may not be informative enough and I cannot (or hope I cannot) reproduce the problem, since the reinstallation included deleting the whole prior installation from the hard drive. Perhaps other users have had similar experience and will add their reports with details. I'm not asking for help with what seems to be a past problem for me but reporting what may be a problem for multiple users that possibly needs a fix for future versions, if the cause can be deduced.