I have done a short and a full scan and this message came up on both. It wont let me do anything with the files
well… very difficult to do anything with files that cant be found. 
anyway, this is just a scan error message. files that cant be scanned for whatever reason are just that, and does not mean they are infected
avast is a antivirus program and will only take action on infected files…not scan errors
infected files when found are given a malware name
files not found error is usually gone if you reboot and scan again…
files that can not be scanned is the most frequently asked question in the forum so a ton of info if you forum search
What operating system do you have ?
It looks like you still have Windows Defender (WD) enabled and this was possibly a WD update and after the update the temp files would be removed. This is speculative as we can’t see the full path to the files, the .…\ concatenation would show exactly were these files are located.