+3  A: 

This is happening when you hit K in normal mode.

     K    Run a program to lookup the keyword under the
          cursor.  The name of the program is given with the
          'keywordprg' (kp) option (default is "man").  The
          keyword is formed of letters, numbers and the
          characters in 'iskeyword'.  The keyword under or
          right of the cursor is used.  The same can be done
          with the command >
            :!{program} {keyword}
          There is an example of a program to use in the tools
          directory of Vim.  It is called 'ref' and does a
          simple spelling check.
          Special cases:
          - If 'keywordprg' is empty, the ":help" command is
            used.  It's a good idea to include more characters
            in 'iskeyword' then, to be able to find more help.
          - When 'keywordprg' is equal to "man", a count before
            "K" is inserted after the "man" command and before
            the keyword.  For example, using "2K" while the
            cursor is on "mkdir", results in: >
            !man 2 mkdir
          - When 'keywordprg' is equal to "man -s", a count
            before "K" is inserted after the "-s".  If there is
            no count, the "-s" is removed.
          {not in Vi}

If you notice, it's running ri in the open window, which is the ruby documentation app. In Unixy environments, the help program normally runs inline, just displacing the vim output for a minute.

Is this using gvim, or command-line vim?

In either case, you can try monkeying with 'keywordprg' to fix the popup

Or, if you can't train yourself not to type it, you can just use :nnoremap K k to change what K does (in this case, just treat it as normal k command and go up one line).

rampion
I am using gVim. Its not just with the letter k. For example, if i have an object name FO_O and I want to change it to MFO_O. Ever letter I type before F opens this window. Please suggest a solution. This is making editing in Vim a torture.
kunjaan
what sequence of commands are you entering to change FO_O to MFO_O? I'd add an addendum to your question, explaining how it happens keystroke by keystroke: e.g. "cursor on F, in normal mode, hit 'i' to go into insert mode, typed 'M', hit <Esc>, then window pops up" or whatever the sequence is. This will help debug your problem.
rampion
+1  A: 

I have this same issue on my work desktop, but not my home machine. The setups are near identical.

While stalking down a possible cause, I noticed that when I leave my cursor over a Ruby symbol such as File, Vim would popup a short description of the File class. After comparing all the various vim scripts and ri-related files that I could find, I finally settled on the only solution that worked...

Open $HOME/_vimrc and add the following line:

autocmd FileType ruby,eruby set noballooneval

Previously, I commented out a block in $VIMRUNTIME/ftplugin/ruby.vim, but Brian Carper suggested a better solution of :set noballooneval. I added the autocmd line so it is only executed with Ruby files.

If anyone figures out a true solution, please contact me. :(

Slackwise
Did you try `:set noballooneval`?
Brian Carper
I have now--updating my post. :P
Slackwise