Well switched McAfee off as far as you can. Although listed in the services start up list McShield, McAfee Validation Trust Protection can be unchecked but they cannot be turned off. You can select apply and then OK and then go back and you see they are checked on again.
Also when running OK I selected the McAfee desktop icon and it came up saying everything was working so I'm not sure whether I really turned it off or not. Or did selecting the McAfee icon turn it on??
Anyhow problem has lessened only two fail to boots against about 5 or successes. Only one failure had an event logged something to do with d\longhorn etc etc which a web search suggested a conflict with Vista gadgets..
So better but not fully cured... thanks for the advice..