[wp-hackers] query_posts tag parameters

[Jason]

Hi All

I am trying to do a basic tag query using the following tag parameters

query_posts(array('tag__in' => array('Marriage') ) );
query_posts(array('tag__and' => array('Marriage') ) );
query_posts(array('tag__not_in' => array('Marriage') ) );

But they don't appear to be working - this is the first time I've tried to
use them so wanted to check:
a) If i doing it properly; and if so
b) If this is a known problem or if it is just me?

query_posts('tag=xxx'); appears to be working so I am stumped.

Using MU latest version.

Thanks in advance.
Jason