Another thing which is driving me batty....

I log in via ssh.  there is a long pause while the 'groups' utility is run.
When I get a prompt I can type  'id  myusername' and get an instant response.
Five minutes later I open a new terminal on my desktop, and it hangs, again in the groups utility

I have set enum_cache_timeout to be 1200.  Should I be looking at other cacehing parameters please?
From my nss stanza:

filter_users = root, postfix, lightdm
filter_groups = root
enum_cache_timeout = 1200
entry_negative_timeout = 600