Hey, you might be interested to know that I managed to fix the problem with my Avast
At first I did a reinstall, but it didn't help, so this time what I did was:
1. download the Avast Removal Tool
2. run the tool from Windows in Safe Mode and uninstall Avast
3. reinstall Avast in a different directory
And now it works perfectly, no shields down since yesterday
Cheers