Why would dsenableroot NOT work on a 10.7.5 OSX Server?
Try: sudo dscl . -passwd /Users/root PASSWORD. Else: a bit-flip hit your disk and corrupted your Directory Services "database" exactly there where the root user's data usually resides. Check this with the usual tools like dscl or even copying the root.plist:

sudo cat /private/var/db/dslocal/nodes/Default/users/root.plist &gt;  ~/Desktop/root.plist


The default root.plist with root disabled looks like this:



The root.plist with root enabled (redacted all hashes etc.):