How can I teach my phone not to capitalise "It's" every time?

I'm using the standard full QWERTY on-screen keyboard on my HTC Desire S, and when typing in to any app it seems that I cannot type it's without manually inserting the ', which is relatively slow and cumbersome, especially considering many other abbreviations work fine (eg, c, a, n, t -> can't). If I type i, t, s then the default word that is presented is its, but in the word selection list I am presented with It's as a second choice; *always* capitalised. it's is not presented as a choice anywhere in the list of suggestions. The phone seems to only capitalise anything else following a full stop or new line, and gets many other abbreviations correct, so why the misbehaviour for it's? And how do I fix it? I've already tried adding it's to the dictionary (and checked that It's isn't there), but that didn't work.