Two identical installs, same database.
localhost/install1 is mapped as abc.com
localhost/install2 is mapped as xyz.com
two directories, two domains, one database
if I point my browser to xyz.com, a cookie is set that expires in three weeks. If I *login*, the cookie becomes a session cookie that expires immediately. bad.
if I point my browser to abc.com, a cookie is set that expires in three weeks. If I *login*, the cookie still expires in three weeks. good.
It's as if there was something about the "xyz" domain that drupal doesn't like.
But here's the kicker:
Two identical installs, *two* databases.
localhost/install1 is mapped as abc.com
localhost/install2 is mapped as xyz.com
if I point my browser to xyz.com, a cookie is set that expires in three weeks. If I *login*, the cookie becomes a session cookie that expires immediately. bad.
if I point my browser to abc.com, a cookie is set that expires in three weeks. If I *login*, the cookie still expires in three weeks. good.
BUT, and this is a big but, if I switch everything around, and map localhost/install1 to xyz.com and map localhost/install2 to abc.com:
if I point my browser to xyz.com, a cookie is set that expires in three weeks. If I *login*, the cookie becomes a session cookie that expires immediately. bad.
if I point my browser to abc.com, a cookie is set that expires in three weeks. If I *login*, the cookie still expires in three weeks. good.