Cross certificates for the client are stored in the clients personal addressbook.
I'd have a look in the PAB for the R6 client and see if there is a cross certificate for /web and if it's there delete it and then try access the server again.
My guess is that it's not the server that you can't access but a database signed with the /web certificate.
Hope this helps,
Declan Lynch.
http://www.qtzar.com