Pasting after 'dd' sometimes pastes vertically
This is probably one of the weirdest bugs.
Sometimes, after working for a while, something triggers this bug. Basically when I delete a whole line using 'dd' and then paste it with p, the line is actually pasted vertically, not horizontally! As weird as it sound here is an example:

This seems to be file-specific, if I try to 'dd' in another file, it works fine (until the bug is hit in that file too).
Strange bug indeed. I'm not able to replicate it on osx 10.9. When you reproduce this what file type are you in? To see if I can reproduce, could you provide your user.keymap, user.behaviors and list of plugins?
If it's easier, you could upload your User plugin to github. It's located at $PLUGINS/User where $PLUGINS depends on your OS - http://docs.lighttable.com/#plugins-directory