@Magnum,
If you can concentrate on sending this to Avast as a possible FP as instructed in reply #3, you could gain some time (instead of passively waiting for someone from Avast Team to see and read this topic).
The "details" (at least for now) is not specifically for "you" (your site), so that's why is not *that* important.
If it is indeed a FP, then Avast will solve this and your friend (and everyone else that has Avast) will be able to get to your site without problems, but for that to happen as promptly as it can, you should probably report this as suggested.