Here is a weird timing related problem (I guess) with winbindd and Samba 3.0.26a, recompiled from source for RedHat EL5, authenticating against Win2003SE2 AD.
I tend to get the error "pam_winbind_request: write to socket failed!" when I run winbindd normally. This leads to "pam_winbind (su -l: auth): internal module error (retval = 3, user = 'root')". This problem doesn't always happen. It changes from day to day.
This problem leads to an enormous system slowdown. Even a simple command like 'ls' will take minutes to execute. I have seen other people complaining about the same thing here: http://www.infrant.com/forum/viewtopic.php?p=67430
If I kill winbindd, the system becomes responsive again, but then I cannot authenticate with AD at all of course.
However, when I run "winbindd -d10", the problem goes away!
I'll try to look into this next week.
OK, since I can compile the source, just let know what you need me to do, to help find the problem. I have been reading code to try and figure it out, but so far I have no idea what is going wrong.
Please reopen if this is still the case with the current Samba 4.0 or 4.1 code base?
Have you consider to use the Apache mod_auth_kerb from http://modauthkerb.sourceforge.net/ instead?