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As for the technical problem: I've reproduced it on my sandbox install, and I see what you're talking about. I think it may have to do with the variable not being flushed before the new value gets written to it. That's a wicked and probably wrong way of putting it, but the symptoms:
1. No value in database + new value being put in through the form --> value gets written to the database correctly. Doesn't matter whether it's a new submission or an old submission without the respective value in db.
2. Value in database + no new selection being made in the form --> nothing written to db, and old value stands correctly.
3. Value in database + selection being made in the form --> writes the word "Array" to the db.
I have a few ideas what to do about that, and I'll probably get a chance to look into it over the next days.
Not promising anything, though.
As for them friggin real estate sharks: I think you might get much more traffic through your site if you drop the word "Buenos Aires" in a prominent position. As far as I can see, it's not really mentioned anywhere --> Google won't send you the people who want to know about that sort of abuse in that place. Perhaps, you can do some semantic search engine optimization with your front page.