I tend to run random games on a secluded machine, which I currently do not have access to, as a result I'm unable to check the name of the file. Did not look too closely at the name, nor the path and location of the so called "mysterious and rare file" by Avast as I was more concerned about the initial security step for my own sake, and to get a picture of the name to more easily distribute. Upon the next step, it did however just call the file "ThisGrandLife.exe", which I deemed to be a result of the file being ran by it.
I checked back on the file at a later point, with hopes of Avast having finished their checks, but they were still checking. I'll have to check back tomorrow and see what happens. Seeing as I keep files as independent from each other as possible and run protective settings on max, it might just be a case of oversensitiveness, or as you say, the first time the file has ever been seen by Avast. :)