Help! New 10.6 installation - spinning beachball at keyboard selection

Hi

I'd be massively grateful for any help.

I've just installed a new retail purchase of Snow Leopard on my Mac Pro (upgrading from 10.5).

The install went fine, system rebooted, showed me the welcome video, chose language, and then when I selected my keyboard (British) the spinning beachball appears and does not disappear.

I've hard rebooted the system twice, and each time it hangs at exactly the same place: select the 'British' keyboard, press 'continue' -> HANG.

I'd be massively grateful for any help or suggestions, as I'm totally stuck until I can get this resolved.

Many thanks in advance.

Jules