I think that that really should be that the repair process completed successfully as there are a number of conditions that have to be met for a repair to even take place.
1. the file has to be one which is covered by the VRDB, commonly .exe files.
2. the file would have had to have been included in a VRDB generation before infection.
3. the type of malware may not actually be repairable, see trojans below.
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, mainly .exe 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.
Sorry I have zero knowledge of Virtual Machine HDDs, if it is possible to get infected ion a virtual drive, I guess it is possible for avast to detect it, though I have no idea how to go about resolving it.