You are describing the exact problem that I see on my 810 beta install, upgraded to RC.
Whatever orbiter I use, selecting audio or video gives a very very long delay, and SOMETIMES goes into what looks like a neverending reload, every orbiter, every MD, with the only cure being a reboot of the core via SSH. I have to turn the MDs off manually, so they aren't shutting down either. Which reminds me, I noticed SSH was slow as well, so maybe this is all down to network slowness once the problems have started.
I am going to do a complete wipe soon and start over with 810 final, and hopefully I won't see this issues again. Sorry Bulek, I realise that doesn't help you very much, but thought I'd share.
We are able to upgrade our 0710 customers to Dianemo 10.10 if they wish to upgrade and we can export their 0710 DB and import it into there Dianemo 10.10 DB. This brings across all of the standard system configs etc. It does not bring across any actual ripped media though.
Unfortunately the LinuxMCE-0710 & Dianemo 07.10 Db's are not compatible so there is no way to import a LinuxMCE-0710 DB into Dianemo... so unfortunately this also does not help you.
All the best