Cat wont use litter tray

[woozer]

I have two lovely cats a 2 year old spayed female and an 11 month old neutered male. Both were perfectly clean and used trays up until 2 months ago when I had the male neutered. Now he will only wee in a litter tray the pooh goes on the kitchen or garage floor (neither are carpeted) We have three litter trays both of which are regularly cleaned out - someone suggested I put catnip in the tray - didnt work.

Both cats are housecats - there is too much traffic and catnappiing in our area to consider letting them out and we have chosen a breed that is known to love being around humans and happy as house cats

Any ideas please - I desperately love the little chap and am at my wits end

[Precious67]

http://www.celiahaddon.co.uk/pet%20problems/ca ts/litter%20tray.html
I thought this link may help, lots of good suggestions so hopefully you will be able to solve the problem. Good luck from one cat lover to another.