I'm sorry for letting this post appear again, I also have the same problem but I resolved. I thought this problem maybe coursed by a third-party
software's compatibility.
This day, after my system finish it's Startup programs and services, I install Avast! Pro and insert my license (yep, I brought today) and when it finished, it's OK. But when I restart my system, I got the 0-day problem as you said. Then I checked my Startup program, I found the
MacType, a text-rendering-enhancing software, I disabled it's auto-launching when system start option (also you can use any method, for me, I use the Task Manager and turn to the Startup page, then disable it), and restarted my system, the my Avast! Pro work again!
Perhaps this original poster will not check this post again, but I think I should still write down this, maybe any other people need it.
Cheers.
Ps: Also I found a related-post in a site,
http://bbs.kafan.cn/thread-1580563-1-1.html (Chinese).
Pss: My OS: Win8 Pro x64