There have been several recent incidents of users receiving warning virus alerts from Avast but then when “Delete/Move to Chest/Repair” options are selected they receive a message similar to the above.
The reason why Avast cannot delete the file is because it is linked to Explorer, which means that you cannot remove the file while still running MS Explorer.
The answer to this problem is to open a Dos window (using the command prompt option in Accessories) and, using dos commands, navigate your way down to the directory that contains the file. Avast will give you the exact location in the error message banner.
When you find the offending file in the directory, often within IE temp folders, choose Windows Task manager and highlight Explorer.exe. Then choose “End Process” and Windows Explorer will close.
Go back to your Dos window and type del and then the filename or just del . which should remove the offending file. Check by then typing dir and see if the file has been removed.
Then ctrl alt del and choose Shutdown or Restart in Windows Task manager.