I just updated to Avast 2014,9.0 2011 from build 2010 and the online security add-ons are still crashing IE 10 and 11. I’m running Windows 7 64 bit with all critical updates from Microsoft installed. I’m having this same problem with one of my Windows 8 (not 8.1) systems also. This crashing happens when streaming video such as news sources or online movies. I’m not running automatic scripts in my LAN settings in the browser or using proxy settings either. IE also acts sluggish even when I’m not running video streaming. Build 2006 does not appear to be having this issue. I’m not sure just yet why the conflict between Avast and IE. I’ve been running Avast since Jan 2006 and I’ve never had issues like this.
Known issues: AOS plugin doesn´t work with "Enhanced Protected Mode" enabled in IE 11
Try turning off protected mode .
If Protected Mode was active AOS wouldn’t load and would be disabled so that I don’t think would be the reason for the crashes of the OP’s browser.
Best solution I can offer is to disable AOS altogether and that should hopefully solve customk’s problem.