Do you ever have one of those evening where you dig yourself a deeper and deeper hole, and end up going to bed hoping the problem will sort itself out on a reboot in the morning and thinking about avoiding a re-install? Well, the morning is now here for me, freshly rebooted box and a freshly re-installed Virtual Server 2005 (Beta 1 as it happens) and the problem is _still_ there. UUURRRGGGGHHH!
The good news is that I sorted the problem out, and solved another problem at the same time. I had a virtual machine with an undo-disk which I'd been moving around to another location on the host drive. When I tried to re-add the machine to the host but it complained saying that a machine of that name already existed. It didn't - I checked, double checked and triple checked, cleaned my glasses and the laptop screen and finally got an independent witness to check again. It really wasn't there.
The answer is semi-hidden away under c:\Documents and Settings\All Users\Application Data\Microsoft\Virtual Server\Virtual Machines where you'll find a number of shortcuts. A couple of shortcuts were referring to machines I no longer had - one of these had the same name as the machine I was trying to add. Simply deleting the extra shortcuts removed the problem.
Co-incidentally, this also solved another problem - the Virtual Server service was taking an eternity to start up (around 3-4 minutes), and causing one of those annoying "At least one service did not start properly...." type of errors on host reboot. Removing those links dropped it back down to a few seconds again.
By the way, nothing to do with Virtual Server, here's a great way to make Mulberry Jam. Bob - if you're reading this, send a couple of jars over to the UK please! The only tenuous link I can think of to this entry is that I got myself out of a "Jam". Bad, I know.