Gmail activating the Avast anti-virus

[Rwy in Sight]

Every time, I open the Gmail, I get a warning from a Avast (the free version) about a contamination (JS:ScriptPE-inf(TrJ) and the object of the contamination is something on google hangouts. The antivirus then asks me to run a smart control but every time I run it, no problems appear. However the next time I open the gmail the problem appears again. I run Windows 8.1 and FireFox 50.1.0 and the problem appears also when using IE.

I am not sure if it is clear but I would appreciate any hints on what is wrong and how I can fix it.

[cdtaylor_nats]

Search for any files with kanecal in the name. If you find them Avast is working and you have a trojan

[Rwy in Sight]

cdtaylor_nats,

Thanks for the suggestion! I did check but nothing come up.