title: Can't use 'mark a' or 'mark A' in vim
body: <p>I like to use vim (on ms windows), I guess everybody have a favorite editor and this is mine.</p>
  
  <p>On one particular PC I run into problems conserning the <code>mark[a-zA-Z]</code> command.
  It does not work for the letters a and A but it does for b-z and B-Z and I would like to know why.</p>
  
  <p>If I use the command <code>:marks</code> I can see that <code>ma</code> and <code>mA</code> do set an entry. But <code>'a</code> and <code>'A</code> have no effect. The same for the backtick versions.
  If I do the same with labels b or B it works.</p>
  
  <p>I checked my _vimrc but there is no line doing something to a or A.</p>
  
  <p>What can block the labels a and A?
  How can I find out what is causing this problem?</p>
  
  <p>Any sugestion is welcome.</p>
  
  <p><strong>Additional information: 5-mar-2016, 23:59</strong></p>
  
  <p>I have no _gvimrc file and use the `standard' _vimrc file, never took the time to dig deep into the vim configurations. So it is still pretty vanilla. I like it this way, there are too many PC's I have to work with and synchronising _vimrc files is not what I'm looking for. :-)</p>
  
  <p>This is in my _vimrc file.</p>
  
  <pre><code>:source C:\Program Files (x86)\Vim\_vimrc
  
  let g:xml_syntax_folding=1
  :filetype on
  :filetype plugin on
  
  :set foldmethod=marker
  :set foldmarker={,}
  
  autocmd FileType xml source C:\Users\andre\vimfiles\ftplugin\xml.vim
  autocmd FileType python source C:\Users\andre\vimfiles\ftplugin\py.vim
  autocmd FileType cs source C:\Users\andre\vimfiles\ftplugin\cs.vim
  </code></pre>
  
  <p>I have tried the suggestions made by cbaumhardt and that does not make any difference, running <code>vim -Nu NONE -U NONE</code>.</p>
  
  <p><strong>Additional information: 6-mar-2016, 20:23LT</strong></p>
  
  <p>The keyboard setting was interfering with the input. (<code>US-international</code>)
  Changing the keyboard setting to <code>US</code> solved the problem.</p>