Do you have your browser set up to delete all cookies when you log off? That could be the source of your problem since your browser stores logon data as a cookie.
Keep getting it? Or keep getting it as in, you had it a month or so ago and it pops up again? The signon cookie is not set to be perpetual, it expires after what seems to be about 60 days or so (if I was more ambitious I’d go look at the cookie in question and get an actual number). So, you log in automatically day after day for a perios of time and then you get the “somethign has changed” popup and you log in again - and then it works for day and days again.
The only thing I find annoying about it is the wording, it’s probably not the best - it’s not always a software upgrade that forces it. But since it’s only like once every other month or so, it’s really not worth the effort to complain about, or even probably to find a fix because it’s probably an issue with the forum software and not MR’s implementation of it.