I added in a new website on my local IIS yesterday, IIS 8.5 on Win 8.1.
After I added it IIS hung indefinitely with the loading circle and I ended up having to kill it
One thing you can try to using a previous configuration, they are stored in
C:\inetpub\history
.
Copy the *.config files to C:\Windows\System32\inetsrv\config
, you may have to use the one before the last one (CFGHISTORY_000000xxxx), the last one is usually the current one.
If that doesn't help, copy those config backups somewhere else, re-install IIS and then restore a config backup.