I changed my keyboard layout to norwegian and and I can reproduce it with ctrl-shift-+. Multibyte editbox must be on, SJIS off and ansi codes off, multibyte display doesn't affect it. Just type something, press trl-shift-+ then type some more (dont hit enter in between, when you use arrow up to get last command, it shows up normal)
For Mentality: keyboard layout to US -> ctrl-shift-= did it here, maybe you have some dvorak thingy or something?
What I also found out during testing: why does ctrl-m act as ctrl-enter? Is that a feature or a bug?