diff --git a/src/calibre/ebooks/pml/pmlconverter.py b/src/calibre/ebooks/pml/pmlconverter.py
index 3fdd627d7e..d2eb2c3736 100644
--- a/src/calibre/ebooks/pml/pmlconverter.py
+++ b/src/calibre/ebooks/pml/pmlconverter.py
@@ -576,10 +576,15 @@ class PML_HTMLizer(object):
                         if indent_state[c]:
                             basic_indent = True
                     elif c == 'T':
-                        indent_state[c] = not indent_state[c]
-                        if indent_state[c]:
+                        # Ensure we only store the value on the first T set for the line.
+                        if not indent_state['T']:
                             adv_indent = True
                             adv_indent_val = self.code_value(line)
+                        else:
+                            # We detected a T previously on this line.
+                            # Don't replace the first detected value.
+                            self.code_value(line)
+                        indent_state['T'] = True
                     elif c == '-':
                         empty = False
                         text = '­'
diff --git a/src/calibre/gui2/actions/choose_library.py b/src/calibre/gui2/actions/choose_library.py
index 001970f9db..d45843995e 100644
--- a/src/calibre/gui2/actions/choose_library.py
+++ b/src/calibre/gui2/actions/choose_library.py
@@ -343,7 +343,7 @@ class ChooseLibraryAction(InterfaceAction):
         db.dirtied(list(db.data.iterallids()))
         info_dialog(self.gui, _('Backup metadata'),
             _('Metadata will be backed up while calibre is running, at the '
-              'rate of approximately 1 book per second.'), show=True)
+              'rate of approximately 1 book every three seconds.'), show=True)
 
     def check_library(self):
         db = self.gui.library_view.model().db
diff --git a/src/calibre/library/caches.py b/src/calibre/library/caches.py
index 2049feaa18..67529397b3 100644
--- a/src/calibre/library/caches.py
+++ b/src/calibre/library/caches.py
@@ -10,7 +10,6 @@ import re, itertools, time, traceback
 from itertools import repeat
 from datetime import timedelta
 from threading import Thread
-from Queue import Empty
 
 from calibre.utils.config import tweaks
 from calibre.utils.date import parse_date, now, UNDEFINED_DATE
@@ -54,7 +53,7 @@ class MetadataBackup(Thread): # {{{
                 (id_, sequence) = self.db.get_a_dirtied_book()
                 if id_ is None:
                     continue
-                print 'writer thread', id_, sequence
+                # print 'writer thread', id_, sequence
             except:
                 # Happens during interpreter shutdown
                 break
diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index 7c8d5aee13..e1a1adc4ff 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -117,6 +117,9 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
     def __init__(self, library_path, row_factory=False, default_prefs=None,
             read_only=False):
         self.field_metadata = FieldMetadata()
+        # Create the lock to be used to guard access to the metadata writer
+        # queues. This must be an RLock, not a Lock
+        self.dirtied_lock = threading.RLock()
         if not os.path.exists(library_path):
             os.makedirs(library_path)
         self.listeners = set([])
@@ -167,10 +170,6 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             return row[loc]
 
     def initialize_dynamic(self):
-        # Create the lock to be used to guard access to the metadata writer
-        # queues. This must be an RLock, not a Lock
-        self.dirtied_lock = threading.RLock()
-
         self.field_metadata = FieldMetadata() #Ensure we start with a clean copy
         self.prefs = DBPrefs(self)
         defs = self.prefs.defaults
@@ -624,6 +623,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
 #                print 'needs to be cleaned'
                 self.conn.execute('DELETE FROM metadata_dirtied WHERE book=?',
                         (book_id,))
+                self.conn.commit()
                 try:
                     del self.dirtied_cache[book_id]
                 except:
@@ -631,7 +631,6 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             elif dc_sequence is not None:
 #                print 'book needs to be done again'
                 pass
-        self.conn.commit()
 
     def dump_metadata(self, book_ids=None, remove_from_dirtied=True,
             commit=True):
@@ -659,6 +658,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             self.conn.commit()
 
     def dirtied(self, book_ids, commit=True):
+        changed = False
         for book in book_ids:
             with self.dirtied_lock:
 #                print 'dirtied: check id', book
@@ -671,6 +671,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
                     self.conn.execute(
                         'INSERT INTO metadata_dirtied (book) VALUES (?)',
                             (book,))
+                    changed = True
                 except IntegrityError:
                     # Already in table
                     pass
@@ -680,7 +681,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         # could lead to a problem because on restart, we won't put the book back
         # into the dirtied_cache. We deal with this by writing the dirtied_cache
         # back to the table on GUI exit. Not perfect, but probably OK
-        if commit:
+        if commit and changed:
             self.conn.commit()
 
     def get_a_dirtied_book(self):