diff --git a/Changelog.draft.rst b/Changelog.draft.rst
index 83cab97..93f64f1 100644
--- a/Changelog.draft.rst
+++ b/Changelog.draft.rst
@@ -26,3 +26,4 @@ Bug Fixes
 
 * Fix python2.6 compatibility with the TTYUI backend (crash)
 * Fix TTYUI regression from 6.5.2 in refresh loop (crash)
+* Fix crashes related to UIDVALIDITY returning "None"
diff --git a/offlineimap/accounts.py b/offlineimap/accounts.py
index fc2687f..ad2015a 100644
--- a/offlineimap/accounts.py
+++ b/offlineimap/accounts.py
@@ -378,7 +378,7 @@ def syncfolder(account, remotefolder, quick):
         statusfolder = statusrepos.getfolder(remotefolder.getvisiblename().\
                                              replace(remoterepos.getsep(),
                                                      statusrepos.getsep()))
-        if localfolder.getuidvalidity() == None:
+        if localfolder.get_uidvalidity() == None:
             # This is a new folder, so delete the status cache to be sure
             # we don't have a conflict.
             statusfolder.deletemessagelist()
diff --git a/offlineimap/folder/Base.py b/offlineimap/folder/Base.py
index 9ff60e2..cab22c2 100644
--- a/offlineimap/folder/Base.py
+++ b/offlineimap/folder/Base.py
@@ -110,13 +110,14 @@ class BaseFolder(object):
         return basename
 
     def isuidvalidityok(self):
-        """Does the cached UID match the real UID
+        """Tests if the cached UIDVALIDITY match the real current one
 
-        If required it caches the UID. In this case the function is not
-        threadsafe. So don't attempt to call it from concurrent threads."""
+        If required it saves the UIDVALIDITY value. In this case the
+        function is not threadsafe. So don't attempt to call it from
+        concurrent threads."""
 
         if self.getsaveduidvalidity() != None:
-            return self.getsaveduidvalidity() == self.getuidvalidity()
+            return self.getsaveduidvalidity() == self.get_uidvalidity()
         else:
             self.saveuidvalidity()
             return 1
@@ -142,7 +143,7 @@ class BaseFolder(object):
 
         This function is not threadsafe, so don't attempt to call it
         from concurrent threads."""
-        newval = self.getuidvalidity()
+        newval = self.get_uidvalidity()
         uidfilename = self._getuidfilename()
 
         file = open(uidfilename + ".tmp", "wt")
@@ -151,7 +152,11 @@ class BaseFolder(object):
         os.rename(uidfilename + ".tmp", uidfilename)
         self._base_saved_uidvalidity = newval
 
-    def getuidvalidity(self):
+    def get_uidvalidity(self):
+        """Retrieve the current connections UIDVALIDITY value
+
+        This function needs to be implemented by each Backend
+        :returns: UIDVALIDITY as a (long) number"""
         raise NotImplementedException
 
     def cachemessagelist(self):
diff --git a/offlineimap/folder/IMAP.py b/offlineimap/folder/IMAP.py
index 75c731c..ffbd6b1 100644
--- a/offlineimap/folder/IMAP.py
+++ b/offlineimap/folder/IMAP.py
@@ -65,17 +65,23 @@ class IMAPFolder(BaseFolder):
     def getcopyinstancelimit(self):
         return 'MSGCOPY_' + self.repository.getname()
 
-    def getuidvalidity(self):
+    def get_uidvalidity(self):
+        """Retrieve the current connections UIDVALIDITY value
+
+        UIDVALIDITY value will be cached on the first call.
+        :returns: The UIDVALIDITY as (long) number."""
+        if hasattr(self, '_uidvalidity'):
+            # use cached value if existing
+            return self._uidvalidity
         imapobj = self.imapserver.acquireconnection()
         try:
-            # SELECT receives UIDVALIDITY response
+            # SELECT (if not already done) and get current UIDVALIDITY
             self.selectro(imapobj)
-            # note: we would want to use .response() here but that
-            # often seems to return [None], even though we have
-            # data. TODO
-            uidval = imapobj._get_untagged_response('UIDVALIDITY')
-            assert uidval != [None], "response('UIDVALIDITY') returned [None]!"
-            return long(uidval[-1])
+            typ, uidval = imapobj.response('UIDVALIDITY')
+            assert uidval != [None] and uidval != None, \
+                "response('UIDVALIDITY') returned [None]!"
+            self._uidvalidity = long(uidval[-1])
+            return self._uidvalidity
         finally:
             self.imapserver.releaseconnection(imapobj)
 
diff --git a/offlineimap/folder/Maildir.py b/offlineimap/folder/Maildir.py
index 95258d9..fe85308 100644
--- a/offlineimap/folder/Maildir.py
+++ b/offlineimap/folder/Maildir.py
@@ -83,8 +83,10 @@ class MaildirFolder(BaseFolder):
         """Return the absolute file path to the Maildir folder (sans cur|new)"""
         return self._fullname
 
-    def getuidvalidity(self):
-        """Maildirs have no notion of uidvalidity, so we just return a magic
+    def get_uidvalidity(self):
+        """Retrieve the current connections UIDVALIDITY value
+
+        Maildirs have no notion of uidvalidity, so we just return a magic
         token."""
         return 42
 
diff --git a/offlineimap/ui/Machine.py b/offlineimap/ui/Machine.py
index ab57ea2..271629c 100644
--- a/offlineimap/ui/Machine.py
+++ b/offlineimap/ui/Machine.py
@@ -70,7 +70,7 @@ class MachineUI(UIBase):
     def validityproblem(s, folder):
         s._printData('validityproblem', "%s\n%s\n%s\n%s" % \
                 (folder.getname(), folder.getrepository().getname(),
-                 folder.getsaveduidvalidity(), folder.getuidvalidity()))
+                 folder.getsaveduidvalidity(), folder.get_uidvalidity()))
 
     def connecting(s, hostname, port):
         s._printData('connecting', "%s\n%s" % (hostname, str(port)))
diff --git a/offlineimap/ui/UIBase.py b/offlineimap/ui/UIBase.py
index 66ecd4f..1cdd94b 100644
--- a/offlineimap/ui/UIBase.py
+++ b/offlineimap/ui/UIBase.py
@@ -309,9 +309,9 @@ class UIBase(object):
     def validityproblem(self, folder):
         self.logger.warning("UID validity problem for folder %s (repo %s) "
                             "(saved %d; got %d); skipping it. Please see FAQ "
-                            "and manual how to handle this." % \
+                            "and manual on how to handle this." % \
                (folder, folder.getrepository(),
-                folder.getsaveduidvalidity(), folder.getuidvalidity()))
+                folder.getsaveduidvalidity(), folder.get_uidvalidity()))
 
     def loadmessagelist(self, repos, folder):
         self.logger.debug("Loading message list for %s[%s]" % (