Let me be clear up front, my main distro is LMDE, but I have many OSs on several computers. I use ssh extensively to connect and control them. Mostly, I use RSA key-pairs and password-less login. I've been doing this for a few years and haven't had any issues for a long time. However, I just added a new OS, the latest Kubuntu, to an open partition. As I said, I mainly work in LMDE, but I like to keep an eye on kde, thus the Kubuntu.
After setting up the keys etc, I logged in to my server, and everything seemed fine. I did some work, logged out, but later tried to log in again. No go?? I got the not allowed message. I tried other terminal tabs, restarting the ssh server, even closing and reopening the terminal.
If I re-import the key, it seems to work...exactly once? I'm completely baffled? I don't think this is a kde issue, because I'm using key-pairs and not the kwallet or anything like that. I'm asking here, because I a lot of smart people hang out here and as I've said already LMDE is my main OS.
Any ideas, how to deal with this?