Frodo library update stuck on 'Preparing...'

Hi.
Have been using Frodo RC1 for a while with no problems. On starting XBMC today, the library update window just shows 'Preparing...' and most actions in XBMC result in it hanging.

I've tried updating to RC2 but the problem remains. Have also tried removing sources to see if I can start afresh, but still just hangs on me.

Any help on sorting this much appreciated.

Ralph