DavidR
2
You fail to give us the most important piece of information, the URL of the site so that it can be investigated ?
What version of avast are you using, Pro/AIS/Premier and the build number, e.g. 8.0.1489 ?
Having said that if it is still the same even with avast disabled - not a great idea disable the web shield as at least you have a fall back - then it is unlikely that there is an avast interaction.