See Bug 190412 for an explanation. The problem is a little broader than the bug reports. See Bug 193085 for a more detailed explanation of the problem.

The problem was me fixing khotkeys…

That is some kind of unexpected comeback from a classic out of the pre kde 4.0 development time. I once managed to break the 'e' key for all when working on khotkeys. Me fixing khotkeys exposed a qt bug. Qt did parse the "Win+e" string from kde 3.x as 'e' because it didn't recognize the Win modifier. It is called Meta in qt. We fixed the symptom because we couldn't fix the cause and…

That's because on some keyboards Alt+PrintScrn is used as Sysreq. You can use xmodmap -pke | grep -i print to check if you are affected. If you get something along the lines of keycode 111 = Print Sys_Req Print Sys_Req Print Sys_Req there is no alt+printscrn for you.

Someone managed to put a really bad hack into kde hardcoding…