Avast spiking huge amounts of memory ...

I’m having sporadic spikes in memory usage. On task manager ‘Avast. service’ was about the normal 10MB on start up. After about 30mins the system was lagging. Checked task manager, … ‘Avast. service’ was @ 400MB. This lasted for around 15mins. I’ve no idea why. The laptop is barely a month old. It’s happened on several occasions.

The laptop came with Norton preinstalled. I used the Norton uninstall tool before installing Avast. Never really had many issues apart from auto update not working which was resolved with a tweak. Windows Defender is showing as disabled.

Using Windows 8