diff --git a/openerp/http.py b/openerp/http.py
index 3c2998699e7..c154330b059 100644
--- a/openerp/http.py
+++ b/openerp/http.py
@@ -1145,11 +1145,14 @@ class Root(object):
     """Root WSGI application for the OpenERP Web Client.
     """
     def __init__(self):
+        self._loaded = False
+
+    @lazy_property
+    def session_store(self):
         # Setup http sessions
         path = openerp.tools.config.session_dir
         _logger.debug('HTTP sessions stored in: %s', path)
-        self.session_store = werkzeug.contrib.sessions.FilesystemSessionStore(path, session_class=OpenERPSession)
-        self._loaded = False
+        return werkzeug.contrib.sessions.FilesystemSessionStore(path, session_class=OpenERPSession)
 
     @lazy_property
     def nodb_routing_map(self):
diff --git a/openerp/modules/module.py b/openerp/modules/module.py
index 505e51b0394..72b87e0bbfa 100644
--- a/openerp/modules/module.py
+++ b/openerp/modules/module.py
@@ -43,7 +43,7 @@ MANIFEST = '__openerp__.py'
 _logger = logging.getLogger(__name__)
 
 # addons path as a list
-ad_paths = [tools.config.addons_data_dir]
+ad_paths = []
 hooked = False
 
 # Modules already loaded
@@ -89,6 +89,10 @@ def initialize_sys_path():
     global ad_paths
     global hooked
 
+    dd = tools.config.addons_data_dir
+    if dd not in ad_paths:
+        ad_paths.append(dd)
+
     for ad in tools.config['addons_path'].split(','):
         ad = os.path.abspath(tools.ustr(ad.strip()))
         if ad not in ad_paths:
diff --git a/openerp/tools/config.py b/openerp/tools/config.py
index 9a054772695..e4205f0b5f5 100644
--- a/openerp/tools/config.py
+++ b/openerp/tools/config.py
@@ -61,7 +61,10 @@ def check_ssl():
 DEFAULT_LOG_HANDLER = [':INFO']
 
 def _get_default_datadir():
-    return appdirs.user_data_dir(appname='OpenERP', appauthor=release.author)
+    home = os.path.expanduser('~')
+    func = appdirs.user_data_dir if os.path.exists(home) else appdirs.site_data_dir
+    # No "version" kwarg as session and filestore paths are shared against series
+    return func(appname='Odoo', appauthor=release.author)
 
 class configmanager(object):
     def __init__(self, fname=None):
@@ -649,7 +652,7 @@ class configmanager(object):
 
     @property
     def session_dir(self):
-        d = os.path.join(self['data_dir'], 'sessions', release.series)
+        d = os.path.join(self['data_dir'], 'sessions')
         if not os.path.exists(d):
             os.makedirs(d, 0700)
         else: