can’t login all of a sudden

i’ll be as specific as possible, since i don’t know that any of the info matters…

this is not a new install, i upgraded to 2.6.1 a couple weeks ago i guess and have been working on my site pretty much daily since…
i was working on it last night (using google chrome) with several tabs open, adding tags to posts… that is, i had installed a ‘random post’ plugin a couple days ago and had several tabs open that i’d hit the button and add tags, hit the button again and jump to another tab while it loaded… i had been doing this for a couple hours or more…

well, suddenly when i went to a tab, there was the login screen… i went to another, same thing… i went to another where a post page was, hit edit and i got the login screen… well, my browser had the login filled in so i hit submit, but it just seemed to reload… that is, it didn’t say incorrect password, yet here i was on the login page again… i did this a couple times and same results…
it was late, i was irritated so i went to bed…
this morning, i did the lost password via email, tried it, and still couldn’t login… sometimes it says i have an incorrect password… btw, i have my blog set so people cannot join, so i can’t even try to register a new account, as i have seen suggested…
i deleted cookies and cache, same results… since i am using google chrome and it hasn’t even been out 24 hours, i went and tried my usual browser, same results – i even tried from my phone, same results…

so, i googled and can’t find anyone with my exact problem and only got a couple pages into the results before i decided i’d just come here ask…

i’ve been using wordpress for a couple years now, through a few versions, on the same host, and nothing like this have ever happened…

anyone have any ideas?