hi just thought this further information might be helpful (sorry i'm not very technical :)
Initially I waited for some time (over 10 minutes) for it to rectify itself, though it didn't so i totally uninstalled the program a number of times before reinstalling, also restarted laptop to no avail. I then deleted the index file and reinstalled the program and it worked fine - though obviously I had to start from the beginning.
So I have tagged now nearly 500 photos (of a total 11,500 which I eventually hope to have indexed) and restarted the program - and it appeared to freeze again, though this time it fixed itself after a short while.
I wonder whether the number of photos that I am importing should be causing this?
Any help greatly appreciated.