Thanks for your reply. It seems to be intermittent as it's working fine at the moment, but it has happened three times over the last couple of weeks.
I had a look at the performance under Task Manager and the CPU usage went up to around 40-50%, but the memory usage went up to 99% when using the Minilab! As it happens, I just received a new memory stick today, so hopefully things will improve.
However, if more memory doesn't fix the problem, I'll come back to you.
Thanks again,
Steven.