Multicolumn index - is there a limit?

Hello all,

In continuing my quest from yesterday to speed up some INSERTs I'm doing, I
came across a SELECT statement in my trigger that is taking .433 seconds to
run.  Here is a sample query:

select * from status s where s.site_id = 18 and s.host_id = 49 and
s.product = 'BETA' and s.class = 'APPS' and s.subclass = 'MONITOR' ;

I had drastically increased performance of some other queries this morning
by adding a multicolumn index on the table, so I thought I would try here
as well.  Here's the table and the index I created:

          Table "status"
 Attribute |   Type    | Modifier
-----------+-----------+----------
 site_id   | bigint    | not null
 host_id   | bigint    | not null
 product   | varchar() | not null
 class     | varchar() | not null
 subclass  | varchar() | not null
 status    | varchar() | not null
 msg       | varchar() |
 tstamp    | timestamp |
Indices: status_5_column_index,
         status_host_id_key,
         status_site_id_key

The query I used to create the index:   create index status_5_column_index
on status (site_id, host_id, product, class, subclass);

I then ran some tests.  It's still taking .433 seconds on average.  Is a 5
column multicolumn index too much for postgres to handle?  Is my query not
using the index at all?  Is my database designed horrendously and the mere
fact that I have a select with 5 where conditions making you ill?  :-)  It
worked for two columns this morning, so I thought I'd give this a shot.

Thanks,
Fran