diff --git a/src/calibre/ebooks/mobi/mobiml.py b/src/calibre/ebooks/mobi/mobiml.py
index 720bb3df8f..afc2fb63ba 100644
--- a/src/calibre/ebooks/mobi/mobiml.py
+++ b/src/calibre/ebooks/mobi/mobiml.py
@@ -140,7 +140,7 @@ class MobiMLizer(object):
         para = bstate.para
         if tag in SPECIAL_TAGS and not text:
             para = para if para is not None else bstate.body
-        elif para is None:
+        elif para is None or tag in ('td', 'th'):
             body = bstate.body
             if bstate.pbreak:
                 etree.SubElement(body, MBP('pagebreak'))
@@ -160,7 +160,8 @@ class MobiMLizer(object):
             elif indent != 0 and abs(indent) < self.profile.fbase:
                 indent = (indent / abs(indent)) * self.profile.fbase
             if tag in NESTABLE_TAGS:
-                para = wrapper = etree.SubElement(parent, XHTML(tag))
+                para = wrapper = etree.SubElement(
+                    parent, XHTML(tag), attrib=istate.attrib)
                 bstate.nested.append(para)
                 if tag == 'li' and len(istates) > 1:
                     istates[-2].list_num += 1
@@ -340,6 +341,10 @@ class MobiMLizer(object):
             tag = 'tr'
         elif display == 'table-cell':
             tag = 'td'
+        if tag in TABLE_TAGS:
+            for attr in ('rowspan', 'colspan'):
+                if attr in elem.attrib:
+                    istate.attrib[attr] = elem.attrib[attr]
         text = None
         if elem.text:
             if istate.preserve:
@@ -377,6 +382,6 @@ class MobiMLizer(object):
                 bstate.vpadding += bstate.vmargin
                 bstate.vmargin = 0
                 bstate.vpadding += vpadding
-        if tag in NESTABLE_TAGS and bstate.nested:
+        if bstate.nested and bstate.nested[-1].tag == elem.tag:
             bstate.nested.pop()
         istates.pop()
diff --git a/src/calibre/ebooks/mobi/writer.py b/src/calibre/ebooks/mobi/writer.py
index 4fb080801e..306f097c90 100644
--- a/src/calibre/ebooks/mobi/writer.py
+++ b/src/calibre/ebooks/mobi/writer.py
@@ -364,7 +364,11 @@ class MobiWriter(object):
         if image.format not in ('JPEG', 'GIF'):
             width, height = image.size
             area = width * height
-            format = 'GIF' if area <= 40000 else 'JPEG'
+            if area <= 40000:
+                format = 'GIF'
+            else:
+                image = image.convert('RGBA')
+                format = 'JPEG'
             changed = True
         if dimen is not None:
             image.thumbnail(dimen, Image.ANTIALIAS)