Downloaded quarantined spyware files can’t be decrypted using QDecrypt.
OfficeScan uses SSAPI (Spyware Scan Application Programming Interface) to deal with spyware. This scan engine uses a variety of internal scanning functions to remove spyware-related files along with the changes these files make in various system areas such as the Windows registry, Program Files shortcuts, and others. Since Spyware cleanup is not file-based only and it may contain multiple file detection, QDecrypt can’t be used to restore files quarantined by SSAPI. It can only be use for files detected by VSAPI (Virus Scan Application Programming Interface).
Use the restore function in Anti-malware instead.