Whoa! That is strange. I'm going to give you some ideas... I'm in no way a professional but I've seen things like that before related to memory or failing hardware. (husband is an ET)
You can try a few things to see if you can figure out what's going. on.
1. Go into device manager and see if there is any hardware issues. (even new computers break down) Look for memory/video, etc... weird things that aren't normal.
2. Double check to see how many programs run automatically. Turn off the unnecessary ones.
3. Check on the latest update for Avast. Roll it back to a previous restore point and see if that brings it back and if it does allow the update again...
Good luck!