If I put a line of kd's on the screen in vim-5.6-7, eg: kd kd kd kd kd All of the kd's except for the first one will be highlighted. In gvim, it is highlighted with a yellow background. In vim, it is highlighted with a brown background. It happens either with or without a .vimrc present.
This is probably not a bug, but the syntax highlighting feature. Apparently "kd" has a meaning in some language and your file is recognized as being of that type. (It's the same as all further characters being highlighted when you use /* in a C file). If you don't like the highlighting feature, edit /usr/share/vim/vim56/macros/vimrc or override it in a local ~/.vimrc.
This is actually because search will highlight all instances of the search pattern on the screen. Combined with this, is the fact that this version of vim will remember your last search pattern and highlight it when you re-open a bug.
That should be "re-open a file" not "re-open a bug". By the way, is there a way to turn this off?