This is a fresh install (server) onto W2K8 with IIS 7.5 per the Adobe ColdFusion 10 Lockdown Guide. My CF Admin section works fine. I created a new site and created an index.cfm file (which is the only default document in IIS). If I browse to www.domain.com it loads the index.cfm file just fine. But, if I go to www.domain.com/index.cfm I get a 404. If I create a .htm page and navigate to it - www.domain.com/somepage.htm - it works fine.
I've checked the request filtering vs. the cf admin site in IIS and both are the same (except for CFIDE/Admin in the admin site). My mapping to the cfform scripts works fine in my new site (www.domain.com/cf_scripts/cfform.js). CFCs called from my index.cfm page work fine (as long as I load it with just www.domain.com and not www.domain.com/index.cfm).