It installs but no access to Options to modify settings
chrome://wrc/content/options.html
just a blank page. Also the big green a is just black.
This is in Windows XP and it was working great with FF 28.
I have exactly the same problem. It is a pity to see that, once again, avast seems to be doing nothing about this. I’m seeing an increasing amount of frustration when I Googled this particular problem as many are suffering from it. It is such a pity as avast used to always work so well but, increasingly they seem to be ignoring their customers. This should be gripped as it is SERIOUSLY damaging their reputation. 
No problems with FF 29.0.1.
Anyways I solved it while I was running FF 29 by reinstalling it and rebooting the comp.
http://forum.avast.com/index.php?topic=150082.0