Control panel url doesnt work since upgrade

[DJSADERS]

Hi,

i install ispcp rc5 on a blank server install a few weeks before rc6 was released the url admin.domain.com worked perfectly and all was good...

however since i done the upgrade from rc5 to rc6 i can no longer access it via admin.domain.com only via the ip which isnt great for security

Any ideas what caused this, i havnt changed any settings and after the upgrade it still said the url could be accessed vis admin.domain.com

The server is debian etch

Thanks