it opens with no errors for me, windows 7 64 bit sigil 6.0.2.
and the code seems intact:
if I add some text and save, the save works OK also. here is a paste from my sigil code view, after loading.
Code:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Sigil vs nbsp</title>
<link href="../Styles/stylesheet.css" rel="stylesheet" type="text/css" />
</head>
<body class="calibre">
<h4 class="calibre1">Sigil and the non-breaking space</h4>
<p class="calibre2">Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>
<p class="ctr">* * *</p>
<p class="calibre2">The above paragraph spacer contains several non-breaking spaces and causes problems when opened in Sigil v6.2.</p>
<p class="calibre2"> </p>
<p class="calibre2"> </p>
<p class="calibre2">This paragraph is separated from the previous one by 2 empty nbsp paragraphs.</p>
</body>
</html>