I have been experiencing a recurring issue with my new Airport Time Capsule and wondered if any one else has experience of this? Quite often when I wake up my iMac (mid 2011 latest Mountain Lion) I get the dreaded "couldn't complete TM backup as backup disk not available", or something like that. Now I know that if I wait a few minutes I will hear the fan noise kick in from the TC (new vertical model) and then TM backup will complete without further issue. I did use to get this occasionally when I used an external USB HD for TM backups but it is far more prevalent with the Airport TC. I am using a gateway modem for the Internet with TC acting as full router. I have checked and rechecked settings and everything seems fine.