HTML_QuickForm upgrade question/story/BC issue

Hi -- This is a quick anecdote about HTML_Quickform, and a question. Basically, I went to bed and my form scripts were working fine -- have been for weeks. ("fine" == submitting as post, showing error messages when necessary, inserting into / updating relevant db tables.) I woke up this morning and all my forms were submitting as 'get', and the required messages (the rules -- 'required', 'enter valid email', etc.) were not showing (although the red *'s that indicate a required field, did show up). The form "errors" array was empty and the form did not submit with or without the required fields being filled in -- meaning, the db was not being updated or inserted into. This was a global change -- from all my test case scripts to my working dev cases -- clearly a singular setting somewhere was affecting multiple scripts that have been valid for weeks. Needless to say, not a happy moment -- I troubleshot a bit and finally tried upgrading HTML_QuickForm from 3.2.2 to 3.2.3, which I had been going to do anyway. Voila, everything worked swimmingly again (posts, errors, db connections all intact). Which is great, I'm set. But -- my question is -- why did 3.2.2 stop working as expected? Is that usual behaviour when a package upgrades? I would think that existing packages shouldn't be affected by a new release. What changed? Did anyone else have this experience? Thanks, s.