We have about 80 systems running ubuntu 12.04 64bit desktop edition. We are facing a strange problem. Everything works fine except that after the monitor goes to sleep, if we don't wake it for long time then it stucks and won't wake up even if we keep pressing any key. But all tty consoles are working. Also i checked the syslog and it was showing the following warning message:
lightdm: pam_ldap: could not open secret file /etc/ldap.secret (No such file or directory)
Also if i pull out the power cable of monitor and insert it back (once the monitor LED goes from orange to black), the screen comes back and this time also the same above message is logged in the syslog. (The message may be totally unrelated to the error but since it was being logged by lightdm i didn't ignore it).
In pm-powersave.log i am getting the following line in the end
/usr/lib/pm-utils/power.d/xfs_buffer false: not applicable.
Also sometimes the following message is being also logged
kernel: [181899.744014] [drm] GMBUS timed out, falling back to bit banging on pin 6 [i915 gmbus reserved]
kernel: [181901.504013] [drm] GMBUS timed out, falling back to bit banging on pin 0 [i915 gmbus disabled] about every 30 minutes.
Could someone please suggest what could be the possible reason for such a behavior.