It messes up the image loading instead? Wonderful... I guess I should have known it wouldn't be so easy.
Yea, I'm pretty Avast is a culprit here. There can always be more than one thing wrong, but when I google this issue I get results from people having this with other Unity-based games who are also running Avast (some who were running Kapersky, which is another antivirus we've had trouble with in the past). Same with the Fatal-error-in-gc error message that we've gotten from a bunch of people; tons of unity games are getting that when run alongside Avast.
Anyway, I'm certainly not suggesting "don't use an antivirus" is the solution here (it's a dangerous internet and all that), but the fact is that part of what antivirus programs do is stop other programs from doing their jobs. Which is fine until it tries to stop a program you didn't want it to stop. At that point the antivirus needs to provide a reasonable way for you to say "please leave that alone", which doesn't seem to be the case here.
So my suggestion is:
1) For diagnosis purposes, uninstall Avast _completely_, restart the computer, etc, and then try the game. If you're still getting problems then apparently something else is going on (or Avast is more tenacious than it appears), though I haven't the foggiest what it would be. If you're concerned about security during this step, perhaps disconnect from the internet first.
2) If running it without Avast works, yea, finding a different antivirus would be something to consider. To my knowledge Avast has been aware of the unity-related false positives for some time and has not resolved them.
