avast can't scan some files

We got a new HP computer with Windows 8 (upgraded to 8.1), and when we run a full scan using avast free, we get a message saying some files can’t be scanned. There are quite a few. We used avast on our old comp. using vista, and never had this problem. Has anyone had this issue?

Can you post a screen shot of those files please, I suspect restore points or the windows old folder if you have recently upgraded to 8.1.