First of all thanks for all the information provided.
So, if I understood everything correctly, the reason for Avast to react was Tynt script?
If so, I've removed it, and looks like the whole Tynt site was moved to 33Across, with new script for the same purpose and a lot of other things. Anyway, at the moment the script is gone, and it should not alert Avast any longer.
Could someone confirm it?