In IE10, once autocomplete is triggered and hints are visible, any character typed will vanish.
I haven't gotten around to installing IE10 yet and unfortunately this problem doesn't show on IE9.
I'll check back once I've figured out a way to install 9 and 10 side by side.
It's not critical on our end, as we're developing features for a product released next year. Just though you should know & hope you'll be able to find the issue before we release :)
Try with the new hinting widget (addon/hint/show-hint.js), which exposes the same interface but is implemented in a less scary way. (It is new though, and not as thoroughly tested, so you might run into other issues.) The old simple-hint code is deprecated.