Hi, I was having the same problem and several hours went by before I finally got it working.
The directory specified in the DAVLockDB directive must have owner and group set to "www" :
# excerpt from httpd.conf file
In Terminal, type:
sudo chown www:www /Library/WebServer/DAVLock
Also, and this was the REAL problem why I kept getting "Could not open the lock database", the directory must be writable by everyone:
So I did this to make it work in Terminal:
sudo chmod 777 /Library/WebServer/DAVLock
And then it worked!. Hope this helps.