Share useres between two installs – cookie sharing

Hi,

I have two installs of WP that share users, my second install is on a sub-domain of the main site. I’ve followed these instructions: http://engine.taffel.se/2008/11/18/multiblog-single-login-in-wp-26/ with no success.

I checked my cookies and they are exactly the same coming from both sites, but still need to log in twice. The instructions I followed are a little old. Has something changed since then?

Thanks,
Scott