It seems the problem was the colour I was using my config file.

mitterlib/ui/ui_pygtk.py

@@ -39,8 +39,8 @@ from mitterlib.ui.helpers import timesince
 
 _log = logging.getLogger('ui.pygtk')
 
-URL_RE = re.compile(
-        r'((?:(?:https?|ftp)://|www[-\w]*\.)[^\s\n\r]+[-\w+&@#%=~])', re.I)
+URL_RE = re.compile(r'(https?://[^\s\n\r]+)', re.I)
+
 
 # ----------------------------------------------------------------------
 # Helper Functions (not related to objects or that don't need direct access to
@@ -493,8 +493,6 @@ class Interface(object):
         message = data.message
         username = data.username
 
-        _log.debug('Rendering: %s-%s', username, message)
-
         time = timesince.timesince(data.message_time)
 
         # unescape escaped entities that pango is okay with
@@ -505,6 +503,7 @@ class Interface(object):
                 self._options[self.NAMESPACE]['link_colour'])
         message = URL_RE.sub(mask, message)
 
+
         # use a different highlight for the current user
         #message = re.sub(r'(@'+self.twitter.username+')',
         #        r'<span foreground="#FF6633">\1</span>',