Always good to hear a problem is solved. 
Keep an eye on it for e.g. the next week and if the problem comes back, let us know here.
False alarm. I got a bit excited.
Just restarted the PC and the same thing has just happened.
So I uninstalled Avast. Ran Ccleaner, malwarebytes and all clear.
Downloaded the latest install from the Avast website and installed it. Then restarted.
Now I am back to where I started. Just turned Avast off for an hour and hey presto, everything is working again.
There is definitely some conflict with Avast's latest update and my PC. I have Win 7, 64bit.
Any ideas would be super helpful.
Thanks
Ash.