On occasion /dev/null on one of my virtual servers goes bad. It becomes:

-rw-r--r--  root root

Which causes all kinds of horrible issues, The quick correction for this is to re-create the device. This should work on most environments including native, OpenVZ, Parallels (Virtuozza), etc.).

sudo rm /dev/null
sudo mknod /dev/null c 1 3
sudo chmod 0666 /dev/null

If all worked correctly then /dev/null will be (as seen with ls -la /dev/null):

crw-rw-rw-  1 root root 1, 3 

I have not found out why this is happening. Since I do not typically run as root there is something very odd going on.