FireFox 1.5 on Windows has the same behaviour. IE6/Win does not have the behaviour of the down jumping QuickEdit, so it works as it should. The jumping QE exists on both a localhost MODx site as well as on an Internet MODx site. QE only jumps in FF and with specific templates.
Wrapping up, it seems like QE has a bug. In FF it has difficulty to determine it’s vertical position when the content div has a margin-top.
I’ll file it as a bug.
So it wasn’t Kubuntu after all (of course not)...
Thanks for all the help!
Bee