IE dhtml spiffycal problem/debug

I have an issue requiring a quick identification of the problem and debug where 2 spiffCal dhtml popup calendars will not populate 2 date fields when using any version of Internet Explorer The solution must not affect the page display in Firefox, Chrome or IE (in other words it must break the layout or any functionality) see the booking form near the bottom of [login to view URL] the form works without issue inder Firefox and Google Chrome and for some reason i cant identify why it doesnt under IE 7 or 8 the page is based on a heavily modified osCommerce installation and uses the STS templates contribution along with several custom modules I need someone who can rapidly sort this issue and want the work completed as soon as possible so have set a short time frame any queries please ask