diff --git a/src/calibre/ebooks/mobi/reader/markup.py b/src/calibre/ebooks/mobi/reader/markup.py
index 73ba09a189..7c3f80fa51 100644
--- a/src/calibre/ebooks/mobi/reader/markup.py
+++ b/src/calibre/ebooks/mobi/reader/markup.py
@@ -11,7 +11,7 @@ import re, os
 
 from calibre.ebooks.chardet import strip_encoding_declarations
 
-def update_internal_links(mobi8_reader):
+def update_internal_links(mobi8_reader, log):
     # need to update all links that are internal which
     # are based on positions within the xhtml files **BEFORE**
     # cutting and pasting any pieces into the xhtml text files
@@ -35,11 +35,16 @@ def update_internal_links(mobi8_reader):
                 for m in posfid_index_pattern.finditer(tag):
                     posfid = m.group(1)
                     offset = m.group(2)
-                    filename, idtag = mr.get_id_tag_by_pos_fid(int(posfid, 32),
-                            int(offset, 32))
-                    suffix = (b'#' + idtag) if idtag else b''
-                    replacement = filename.split('/')[-1].encode(
-                            mr.header.codec) + suffix
+                    try:
+                        filename, idtag = mr.get_id_tag_by_pos_fid(
+                            int(posfid, 32), int(offset, 32))
+                    except ValueError:
+                        log.warn('Invalid link, points to nowhere, ignoring')
+                        replacement = b'#'
+                    else:
+                        suffix = (b'#' + idtag) if idtag else b''
+                        replacement = filename.split('/')[-1].encode(
+                                mr.header.codec) + suffix
                     tag = posfid_index_pattern.sub(replacement, tag, 1)
                 srcpieces[j] = tag
         raw = b''.join(srcpieces)
@@ -298,7 +303,7 @@ def upshift_markup(parts):
 
 def expand_mobi8_markup(mobi8_reader, resource_map, log):
     # First update all internal links that are based on offsets
-    parts = update_internal_links(mobi8_reader)
+    parts = update_internal_links(mobi8_reader, log)
 
     # Remove pointless markup inserted by kindlegen
     remove_kindlegen_markup(parts)
diff --git a/src/calibre/ebooks/mobi/reader/mobi8.py b/src/calibre/ebooks/mobi/reader/mobi8.py
index 8040a89e15..cdbea325fa 100644
--- a/src/calibre/ebooks/mobi/reader/mobi8.py
+++ b/src/calibre/ebooks/mobi/reader/mobi8.py
@@ -34,6 +34,16 @@ Elem = namedtuple('Elem',
 FlowInfo = namedtuple('FlowInfo',
         'type format dir fname')
 
+# locate beginning and ending positions of tag with specific aid attribute
+def locate_beg_end_of_tag(ml, aid):
+    pattern = br'''<[^>]*\said\s*=\s*['"]%s['"][^>]*>''' % aid
+    aid_pattern = re.compile(pattern, re.IGNORECASE)
+    for m in re.finditer(aid_pattern, ml):
+        plt = m.start()
+        pgt = ml.find(b'>', plt+1)
+        return plt, pgt
+    return 0, 0
+
 class Mobi8Reader(object):
 
     def __init__(self, mobi6_reader, log):
@@ -148,6 +158,7 @@ class Mobi8Reader(object):
         for skelnum, skelname, divcnt, skelpos, skellen in self.files:
             baseptr = skelpos + skellen
             skeleton = text[skelpos:baseptr]
+            inspos_warned = False
             for i in xrange(divcnt):
                 insertpos, idtext, filenum, seqnum, startpos, length = \
                                     self.elems[divptr]
@@ -156,6 +167,23 @@ class Mobi8Reader(object):
                     filename = 'part%04d.html' % filenum
                 part = text[baseptr:baseptr + length]
                 insertpos = insertpos - skelpos
+                head = skeleton[:insertpos]
+                tail = skeleton[insertpos:]
+                if (tail.find(b'>') < tail.find(b'<') or head.rfind(b'>') <
+                    head.rfind(b'<')):
+                    # There is an incomplete tag in either the head or tail.
+                    # This can happen for some badly formed KF8 files, see for
+                    # example, https://bugs.launchpad.net/bugs/1082669
+                    if not inspos_warned:
+                        self.log.warn(
+                            'The div table for %s has incorrect insert '
+                                'positions. Calculating manually.'%skelname)
+                        inspos_warned = True
+                    bp, ep = locate_beg_end_of_tag(skeleton, aidtext if
+                        isinstance(aidtext, bytes) else aidtext.encode('utf-8'))
+                    if bp != ep:
+                        insertpos = ep + 1 + startpos
+
                 skeleton = skeleton[0:insertpos] + part + skeleton[insertpos:]
                 baseptr = baseptr + length
                 divptr += 1
@@ -320,6 +348,7 @@ class Mobi8Reader(object):
     def create_ncx(self):
         index_entries = read_ncx(self.kf8_sections, self.header.ncxidx,
                 self.header.codec)
+        remove = []
 
         # Add href and anchor info to the index entries
         for entry in index_entries:
@@ -332,11 +361,20 @@ class Mobi8Reader(object):
                 idtag = self.get_id_tag(pos).decode(self.header.codec)
                 href = '%s/%s'%(fi.type, fi.filename)
             else:
-                href, idtag = self.get_id_tag_by_pos_fid(*pos_fid)
+                try:
+                    href, idtag = self.get_id_tag_by_pos_fid(*pos_fid)
+                except ValueError:
+                    self.log.warn('Invalid entry in NCX (title: %s), ignoring'
+                                  %entry['text'])
+                    remove.append(entry)
+                    continue
 
             entry['href'] = href
             entry['idtag'] = idtag
 
+        for e in remove:
+            index_entries.remove(e)
+
         # Build the TOC object
         return build_toc(index_entries)