Shockwave advice about disabling anti-virus programmes works for me and I can now progress beyond the loading screen. It is obvious that my Radeon 9600 128MB is not cutting it - too many lock-ups in the game result in having to re-fly the session, and only in 860X600X32 3D res., and 1024X768X32 in campaign. A Radeon 9600 256MB or similar must be an improvement so I'm looking around at present.
'Find your enemy and shoot him down - everything else is unimportant.'
