Problem moving RS Virtual Directories

I installed RS using the default settings (but without SSL) and it worked fine. Then I installed SP1.
Initially installed to:
http://www.ourdomain.com/reports
http://www.ourdomain.com/reportserver
Then I attempted to move the virtual directories to take advantage of SSL and everything stopped.
So in IIS I created a new web site using a sub-domain:
http://reports.ourdomain.com and loaded a certificate.
Then I saved the 2 original virtual directories as config files and then re-installed them under this new web site e.g.
https://reports.ourdomain.com/reports
https://reports.ourdomain.com/reportserver
I then edited the config files RSWebApplication.config & RSReportServer.config with the following changes
<UrlRoot>http://OurServerName/ReportServer</UrlRoot> --> <UrlRoot>https://reports.ourdomain.com/ReportServer</UrlRoot>
<ReportServerUrl>http://OurServerName/ReportServer</ReportServerUrl> --> <ReportServerUrl>https://reports.ourdomain.com/ReportServer</ReportServerUrl>
And now nothing works... I get the "Server Error in '/REPORTS' Application." error i.e. an aspx error with nothing logged in the RS log.
Something I suspect is that changing the URL from the servername to the domain name is making the permissions act differently - but while its getting the aspx error I can't see what is going wrong. I can't even seem to make it give me the full error. Its giving me the standard:
"Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off"."
And even though the custom errors tag is set as specified its not giving me any error information.
Has anyone any suggestions as to what might be going wrong?

see if this article helps. there are a couple little weird thingsyou need for the virtual directories to work that you might not expect:
http://www.sqljunkies.com/Article/525B575A-7F61-483A-AC8F-FEC700C34674.scuk