Wow, actually, the flashplayer for all my other browsers works okay, but not on this one browser, which is a separate, special use copy of Seamonkey Portable.
I'm really hesitant to uninstall flashplayer for the entire OS when it might just be a gliche in the one browser.
Maybe I'll just reinstall the browser.

Or actually, with flashplayer nonfunctional for the one special use browser, which isn't needed in that browser anyway, maybe it actually makes the browser safer from flash-based attacks.
Yeah, I know, 'sour grapes'; but maybe I don't need to fix it in the one browser after all.

There are so many PUPs lurking in the wild it isn't even funny.
DonationCoder is like a big comforting camp fire in the forest at night, with glowing pairs of evil eyes watching from all around in the outer darkness. o_O

She'll come and sit beside me and reach out and touch my forearm with her forepaw to get me to brush her.
If I ignore her because I'm busy on the computer, she'll keep doing it.  ;D

Seamonkey ran a new update after I posted this thread, and the next time I logged into the problem site, Seamonkey prompted me if I wanted to save the password, so the problem got fixed by a Seamonkey update.