Symptoms: A healthy hive with lots of angry bees.
 
Diagnosis: Your queen is a bitch!
 
Cure: Requeen.
 
Requeening is always a tricky exercise, whenever you attempt it.
Chances of success are lessened with increased population, hence the
best time to requeen is early spring or late fall.  Most literature will
suggest that you introduce a new queen into a nuc made up of frames from
the hive to be requeened.  The new queen is introduced to the nuc box
(which is of course queenless).  When the bees in the nuc have accepted
the new queen, the nuc should then be reunited with the original hive
using the newspaper method, after the original queen is killed and
removed from the hive.
 
This method requires a good deal of manipulation, first to set up a nuc
and introduce a new queen, then finding the original queen in the old
hive to remove her, and uniting the nuc and hive after the new queen is
accepted in the nucleus.  All these manipulations will be made harder by
the fact that your hive is ill-tempered in the first place.  My advice is
to wait until the fall, after the honey harvest.  Some of my largest
yields have come from my nastiest hives.  Then, since you waited
that long you may wait until spring to attempt to requeen.  A failed
attempt to requeen in the spring can be corrected by the bees themselves
(they can rear a queen on their own from eggs laid by the former queen),
whereas a failed attempt in the fall will ultimately lead to a failed
hive.  Late in the season is not the 'proper' time for a hive to raise a
new queen, so if a fall attempt fails, so will your hive.
 
Hints for locating the queen:  She will be in the vicinity of current
queen activity (ie closest to the newly laid eggs).  If you pull frames
filled with stores, you will not find the queen on these frames.  If you
pull a frame with sealed brood, the queen will probably not be on these
frames either.  However, if you pull a frame with newly laid eggs,
chances are high that the queen will be on this frame or one adjacent to
it.  Try to 'scan' the frame rather than 'examine' it.  It is easier to
have the queen 'pop out at you' as opposed to examining every inch of a
frame in an attempt to locate the elusive queen.  Practice on any
"Where's Waldo" book!
 
Good luck!