First do no harm, delete is never a good first decision, move to the chest and investigate as you are doing now.
There is no rush to delete anything from the chest, they can't do any harm there. Anything that you send to the chest you should leave there for a week or two. If after that time you have suffered no adverse effects from moving these to the chest, scan them again (inside the chest) and if they are still detected as viruses, delete them.
viruses in the C:\System Volume Information\ (part of system restore), _restore points are protected by windows and can't be removed in the normal way, you will need to disable system restore and reboot. If after another scan you are then clear you can enable system restore again.
Repair is often greyed out as it isn't available, either the files aren't protected/monitored by the VRDB. Trojans generally can't be repaired (either by the VRDB or avast virus cleaner), because the entire content of the file is malware, so it is either move to chest or delete, move to the chest being the best option (first do no harm). When a file is in the chest it can't do any harm and you can investigate the infected warning.
The VRDB only protects certain files, .exe, dll and other system files, it doesn't protect data files or all files, it is not a back-up program, so there are going to be many occasions where repair won't be an option.
Only true virus infection can be repaired, e.g. when a virus infects a file it adds a small part to it, provided that file is one that avast's VRDB would monitor and you have run the VRDB, then it may be possible to repair the file to its uninfected state.
However, for the most part so called viruses, trojans (adware/spyware/malware, etc.) can't be repaired because the complete content of the file is malicious.
Is your OS up to date, SP2 with all later updates (as RPCexploit would usually mean your OS isn't up to date) ?
Do you have a firewall, if so what ?
