When using rbf_showOrHideField("fieldname",true/false) API in a script component on a page, there are a couple of bugs... 1) After you hide, then show a Checkbox field, the label gets removed (but the checkbox is still present). 2) After you hide, then show a Picklist field, the field gets removed (but the label is still present).
Thanks for pointing this out, we will take a look and get back to you. If it is indeed a bug it will be queued for the next update.
Matt