Avast started to go nuts tonight

[japp]

Each time I start windows explorer Avast turns up with messages as in attached file. There is no way to get rid of this (except for turning Avast off) as I've both tried to open in sandbox and normal. Any suggestions?

Update  engine and virus definition: 120223-1
Program version: 7.0.1407
Running on W7 64-bit

[.: L' arc :.]

Do you have a modified version of explorer.exe, say for example, you used a modified theme in your PC?

[japp]

No.
It also does a similar thing with Redefine.exe.
But today I get the window to decide whether to "open in sandbox" or "normally" for both programs.

[.: L' arc :.]

The behavior is odd. Let's see if there is something malicious messing with your system files.

Download Malwarebytes Antimalware here. Install it then run a quick scan. Please post back the report. Should there be any serious infection, a trained malware expert will join this thread to help you.

[AntiVirusASeT]

u can also download virustotal uploader https://www.virustotal.com/documentation/desktop-applications/

select the offending process within virustotal uploader to upload it for the many scanners to scan it

post the url result of virustotal here