Some information wouldn't go amiss, virus name and original infected file name and location example (C:\windows\system32\infected-filename.xxx)?
It is possible to Repair whilst inside the chest. However, not all files can be repaired, first it must be a file that avast's VRDB process would scan and has scanned.
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.
