Checkbox rendered unclickable in one HTML page but not the index linking from same jQuery

I'm working with a pre-existing index & check out page (so bare with me, I'm editing this code) - both require a checkbox to be checked in order to proceed to the next page, however the checkout page's checkbox is uncheckable. I think both the index and checkout pages are drawing from the same jquery file which is why I can't figure out why just the checkout page's isn't working.

<input type="checkbox" name="agree_terms" id="agree_terms" style="float:left; margin-top:2px;" class="chk validate[required] radio" />

This is the html from the checkout page, which is identical aside from the style to that of the index page. Any suggestions of places I should look that could be rendering the checkbox unclickable?