[eluser]TheFuzzy0ne[/eluser]
I've never heard of this problem before, but in the meantime, I'd recommend you create a custom validation function for your select box, and see if that helps. If not, it should help you debug the problem a bit better.
CodeIgniter loops through the rules and grabs the data accordingly, it doesn't loop through the $_POST array directly. This means that every validation function for any given field is run in sequence until one fails. In your case, it should be failing on 'required'.
Just out of interest, does it make any difference if you put the 'required' rule before the trim? It makes sense that you only trim it once you've confirmed there's actually something to trim.
