This is not a problem for me any more, I'm just posting it in case anyone else runs into it. Maybe it'll save someone some grief.
Last Sunday, I woke up and got my coffee and rather sleepily tried to get online to check my mail. I usually shut my broadband connection down at night. This morning, it told me that my username and password was invalid. Figuring the system was down, I went away and tried later in the day. No luck with either my desktop or my laptop.
I called my ISP who was convinced that the problem was my modem, or my IE settings etc in spite of the fact that I assured him that nothing had changed between the night and the morning.
To make a long story short, he told me I had to wait three days til they could 'escalate' the problem.
When three days passed the ISP called me (!) and after some discussion, she went away to talk to her colleagues. I could connect with a test username and password, but not with my own. This was unusual.
When she came back, she said that I had been having a 'stale session'. Apparently,my computer had a minute drop off in power so that my ISP picked me up as having not logged off when in fact I had. Everytime I tried to log on after that, the system picked up the log on attempt as an attempted hack and refused entry. So they reset it, I pulled my modem off the computer for a few seconds and plugged it back in and all is well now.
I had never heard of a stale session before. Has anyone else?
Anyways, for what it's worth..