Don't mean to intervene here. Just a thought. Have you tried a scan with Malwarebytes? Sometimes malware/virus can cause an install problem. Maybe it is something that avast doesn't recognize. I'm just throwing out suggestions here trying to narrow something down. Is there any other process that is using a great deal of your processor other than avastUI? Maybe there is something else running that avast doesn't quite know how to deal with??
If you don't mind, would you please attach your avast5.ini file? (programdata/Avast software/avast) I would like to compare this file with mine to see if there is something that may stand out.
Will you list your startup programs? Also, what about using diagnostic startup in msconfig to see if it is something at startup that is causing this?
Also, a custom install excluding the sandbox may work. Since the autosandbox was revamped. Maybe it is the autosandbox causing some type of looping.
Since you can't open your GUI, can you go to the avast5.ini file and change the "autosandboxenabled" value to 0? This is just a hunch I have. It disables the autosandbox. See attached.
Ok, I'm done. All yours Tech.
