Yikes! Emacs line mode went crazy and its persisent...please help!

[butzwonker@gmail.com]

Is that even possible? After years of using Emacs, today I might have pressed some presumably incorrect keyboard combination and now Emacs in AucTex has started to go crazy. I used to have visual-line-mode and line numbering on. Now suddenly it wraps to some column (98) instead of the window with and if I press ctrl-e it jumps to the next line. When I go back with ctrl-b it doesn't jump to the last word on the previous line but to the last position in the visible frame! Then, when there is e.g. "the" on the current line and I type " dude", "the" jumps to the previous line and "dude" moves to the beginning of the line.

Also, the line numbering now shows one line per paragraph instead of consecutive line numbers for each soft-wrapped line. 

What's puzzling me is that I did not make any changes to default.el or .emacs and nevertheless the change is persistent across Emacs launches and even logging in and out again. It happened from one moment to the other, so it must have been caused by an unusual keypress.

Does anybody have an idea what I inadvertently changed? Please help, this is driving me nuts and I can't work that way.

GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2017-09-20 on lcy01-07, modified by Debian