If you can get to this link then you can run the "McAfee Virtual Technician" which should find problems with McAfee and help you fix them.

If not, then you can get the McAfee Consumer Product Removal tool. This will completely remove all 2005 onwards consumer McAfee products from your computer regardless of whether the uninstall is broken or not.

I certainly wouldn't recommend going round deleting files manually as even a partial corruption or uninstall may leave system components dependent on something you might delete!

Active Shield is the on-access scanner part of McAfee. Basically whenever you run a program it is intercepted by Active Shield which checks it for known malware before it is allowed to run.

If you use MCPR then you can either reinstall McAfee from the installation discs or install the superiour free products off the net (Avast! or AVG for Antivirus, Zone Alarm for firewall etc..)

After many hours online to the Mcafee help centre, I think its finally sorted. Basically I had to go into safe mode, then uninstall all of the mcafee products on my pc (using a tool they sent me) then reinstall them all again.
I had previously tried this but not in safe mode and it didn't work but seems to be ok now.
I've been told by NTL that mcafee can cause a lot on conflict and so I think I wont renew my subscription next year.
Thanks to all who posted