There have obviously been some big changes from 6 to 7.
In FC6 I set the application.url.fileRoot in _serverSpecificVarsAfterInit.cfm and that seems to be enough.
But after updaing to FC7, a bit of hair pulling and stepping through the code, it looks like you need to re-init the cdn as well now.
Ergo, my entry in _serverSpecificVarsAfterInit.cfm now looks like this:
<cfset application.url.fileRoot = "#application.url.webroot#/mynewlocation/files"> <cfset application.fc.lib.cdn.init()>
I’m not sure if I’m doing this right (someone may haveanother suggestion) but I though I’d put it here in case someone else comes across the same issue.