Since natty, apparmor denies evince (nautilus thumbnailer) access to network drives. This results in long delays and PDF thumbnails not displaying.
Edit /etc/apparmor.d/usr.bin.evince like this (insert the nameservice-line):
/usr/bin/evince-thumbnailer { #include <abstractions/evince> #include <abstractions/nameservice> :
Then do
$ sudo apparmor_parser -r /etc/apparmor.d/usr.bin.evince
Thumbnails should now display again, and without delay.
Ref: https://bugs.launchpad.net/ubuntu/+source/evince/+bug/778638
~~LINKBACK~~