any kids?
any other cat(s), dog(s)?
asked the vet what the problem might be?

Hi,

DO go back to the cat shelter and ask their advice; they knew the cat before
you did and may be able to help.  They will also appreciate that you're
trying to help the cat and not just give up.

In the meantime, provide a separate 'peeing' litter box ... mop up her
accident pee with kitchen roll and put this in the pee tray ... then put
kitty in the pee tray and say 'Good boy' with loving encouragement.  Praise
him everytime he uses the tray.  Start regular toilet training (as you would
with a kitten): after every meal and every sleep, put kitty in the pee box
and say 'Good boy'.  This will pay dividends.  His litter trays should
always be kept in the same place, so he knows where they are.  They should
never be behind a closed door, so he cannot use them when required.

As far as you are able, remove or thoroughly clean anything your cat has
already marked with pee.  To avoid kitty jumping on your furniture, give him
at least one, soft, cushiony bed that is his alone.  He may then not feel
the need to commandeer and territorily mark 'beds' which are not his.   I
have always trained my cats to keep off furniture and not to go upstairs or
in the downstairs larder.  They know these rules well now.  It took a few
months of hard training and praising correct behaviour, but I have no
behavoural problems now.

I really do sense that you want to help and keep this cat.  Please talk to
the cat shelter, and be as patient as you can.  It will come right.

Best wishes,
Spider

You said before that the vet also found crystals in the urine, is that
issue cleared up as well?

Last time you posted I made some suggestions, how many of those things
have you tried?

Here's my previous list (again)of things to try again --

Keep the litter boxes clean, scoop at least once a day, *every day*.
get more boxes, at least one per cat, if it's a multistory house have a
couple of boxes available on each level.
if the litter boxes have covers, leave the covers off  
get a larger litter box, especially if he's a big cat
try different types of litter, most cats seem to like the scoopable
clumping stuff

All I can add, is to keep the cat confined to a small area, best would be
a bathroom where's there's no furniture or other soft stuff he's going to
want to pee on. Keep him in there with food, water, and litter boxes. Try
different types of litter, covered & uncovered boxes. Once you've figured
out what he wants as far as litter and boxes, you're going to have to
leave him in there for a while to re-establish reliable litter box
habits. While the cat's in his enclosed area, go through the house and
clean all the spots he's soiled, so he's won't be attracted back to those
spots in the future. Nature's Miracle works to get rid of the smell.

Had similar problems with one of my cats, but seem to have solved them.
He may have territorial issues and is marking because of that, which is what
my cat was doing.
What helped mine was using a spray that is made by Hartz called "Stay Off
Training Aid." The instructions say to clean the soiled area well to remove
the odor, which, if not removed will encourage him to return to "freshen" up
the marking. Then spray the training aid on the area. The spray has to be
refreshed daily until the animal stops returning, which could take about a
week.
After that if the animal pee's somewhere resume the treatment until the
habit is again broken.
There is some smell associated with the Training Aid but it is not
objectionable and certantly better than cat pee!

It sounds like the UTI was stress induced and it could be that your cat
is one that suffers from a chronic inflammation of the bladder that is
exacerbated by stress. This condition is called interstitial cystitis
and is very uncomfortable for cats and whill cause them to pee outside
the litterbox. It mimics a urinary tract infection but no bacteria is
found. I wrote a post on how to deal with this condition that you can
find here:
http://groups.google.com/group/rec.pets.cats.health+behav/msg/bd3b3a15237b50b0

Pay special attention to the part about Cosequin (glucosamine) and get
your cat on it ASAP. It takes awhile to build up so don't expect it to
work overnight. Also definitely get some Feliway plug-ins to help reduce
the stress level.

In the meantime, it is best to isolate the cat for awhile to one room
with at least two litterboxes. Once he is using the litterboxes for a
good period of time, you can start to let him out slowly for short
peiods of time into the rest of the house, supervised, to see how he
does. Once you are able to allow him out all the time, make sure that he
has easy access to litterboxes and that you have them in several
different areas. Also check out this article:
http://community.webtv.net/getcathelp/litterbox

Megan