WinSer2003, Win2k, Win95, WinVista, WinXP, Windows Server 2008, Windows 8, Windows 7, Win98, WinNT, WinMe
SONAR.Cryptlck!g128 is a heuristic detection that is designed to detect known variants of the Ransom.Cryptolocker family of threats.
Disable System Restore (Windows Me/XP).
Update the virus definitions of your antivirus product.
Run a full system scan.