Some other things to mention on the sticky-login business ...
... double-checked the browser is accepting the cookies - it is
... double-checked the .htaccess file issue; renaming as .bak doesn't alter the login page behaviour
... checking in the admin table after running the query, the password/login do change each time the query runs
There's probably going to be sthg mindnumbingly obvious that solves this in the end.
[BTW I'm beginning to have doubts about the apparent (lack of) functionality of MyphpAdmin at this host - being my first encounter with it, I've no idea what's supposed to be here or how to get at it - but squinting hard at thumbnails of the screen presentation options on the 'Welcome to MyphpAdmin' page, it looks like the LH sidebar with several functions on has gone MyAWOL. There's no obvious way of doing anything other than through MySQL (which is why the admin query was run from there ... )]