I think from the responses that I will stick to version 6.0.1203 until someone manages to sort the problem out. I've checked windows memory dump and have 6 items in there, the last one being from 2007. The only thing I have different on my system for this update that I didn't have before is Malwarebytes, but this doesn't run until I execute the program (as far as I'm aware). The only other thing that I think I did was, after the update, to click the option on avast for it to reboot straight away. I normally leave it until next time I start the PC. Will keep checking back on the site to see if anyone comes up with any reasons for the problems, but won't bother to uninstall and reinstall as it doesn't appear to have worked for a number of people.