Hi hagar,
Thanks for coming back with such a comprehensive reply. Let me explain exactly what has happened. I fly regularly in multiplayer with a squad, finished a nights flying then this problem ocurred on next use. To be certain of using a fresh CFS to fix the problem i did a typical install in a new directory. Both the old and the new have the same problem. I don't want to be paranoid, but a lot of my squad have had their comps hacked while on the zone and have had all sorts of problems........ although I can't think that a brand new installation would carry the same bug...even if it were possible. I have looked in the config.sys but can't seem to find a line that might enable/disable multiplayer.
As you are an expert on CFS1, it worries me that you have never seen this problem before

..................... I always end up having unsolvable problems!..........Lol but I have got to solve this one even if it means buying a new comp.
Thanks for your help.......................so far...............If you think of anything else I am all ears.
Ivor