Hi there.
I bought GDT a couple of days ago, and was really enjoying it. I played a couple or hours ago, but when I tried to start again this evening, AVAST registered it as a ‘suspicious file’. I tried to add it to the exception list,but it seems to have deleted the program file. On trying to reinstall it I get a ‘suspicious file’ warning that won’t let me choose the ignore button and the installation fails. Any ideas what’s going on with that? Dead End Games was on the verge of greatness!
Same here. Came suddenly with the last Avast-Update 
But i didn’t reinstall the game, only restored the exe via Avast.
yep, same problem, just bought the game but i cant play it
If you go into Avast’s virus chest, right click on the GameDevTycoon file and submit “Send to Virus Lab”. A little window will pop up, check “Report as False Positive” and then just fill out some general information.
This is honestly the best way to fix this. Avast releases updates regularly, so I would expect this to be resolved soon. Until then, I would suggest turning off Avast’s shields temporarily by right clicking the icon, you’ll find the option there. Turn them back on when your done playing. Check regularly to see if Avast has released an update that fixes this issue.
Please see my post here on creating an exception for Avast;
Also you may want to temporarily disable Avast while you download and install Game Dev Tycoon.
We got an answer from Avast:
False positive detection. We are sorry. Our virus specialists have
been working on the problem and our virus definitions will be updated.