Do you mean you can’t reach Chest (Quarantine) because it’s not well installed?
Chest is not for download…
If repairing works you don’t have to uninstall/install.
Do you have any other antivirus installed in this computer?

We will need more information to be able to help you:

  • Which OS are you using? Is it up to date?
  • What avast! version and VPS file (virus database) number?
  • What was the filename and path where the virus was found?
  • Which actions have you taken to try solving the problem?
  • Do you use a firewall? Which one?
  • Any other security programs that could interfere?
  • Any useful information into Control Panel > Administrative Tools > Events, specially ‘Errors’.