Strange. Thats the version for pm27 that works. Could be the way the 64bit version is built. I don't build any 64bit releases, and am not sure whats enabled/disabled. You could always just use a hosts file in /etc/hosts to block ads. That's what I do, and it blocks ads/malware system wide. No need for a browser extension. I use the one from here:
http://winhelp2002.mvps.org/hosts.htm
Just rename HOSTS to hosts and cp to /etc then reboot.
Cheers