Situation seemed to fix itself. A couple of BM5 reboots (at one stage, I saw a Windows 'this program is not responding' warning on my TV ;) later and all is fine and working again.
I'd be very impressed with this BS5 setup if it had a two-way remote facility. At the moment it's a bit like using a single CD player! You go over to the BS5, choose your CD, listen and go forward/back through the album tracks with your remote. I guess sw updates will bring the ability to create playlists and so on.
It's just a shame they didn't make this a central hub for ALL media. It could easily handle 720p HD video.