I rescued two cats 6 months ago, and from the start one of them has cried loudly at night - usually every hour or so, either until she tires herself out or until one of us talks back to her. She has good, water, litter, and an open plan house to run round with plenty of toys in. Her sister/mother (we still aren't sure how they are related) completely ignores her so I know it can't be too serious, but my god she sounds like she is hysterical!
We have tried allowing access to our bedroom, or rather I do when OH is away - makes no difference. We tried leaving a light on for her too. I'm not so much worried for her health/sanity anymore as for the neighbours, who MUST be able to hear. Plus we have a baby due in 2 months and I don't want to end up with two 'babies' in the house whose cries I can't understand!
Does anybody have any clues? She never cries like this any other time, unless she is getting her food late on an evening and I am being too slow at dishing it up. The only thing that shuts her up now is shouting down to her - not telling her off (makes her louder) but just letting her know we're awake IYSWIM.