Same thing started happening to me. Even though my preferences are set to start with Windows startup, CHS does not start. If I start CHS myself, the tray icon flashes, but the program does NOT run.
Alt-Tab does not reveal anything. BUT, ClipboardHelpAndSpell.EXE does show up as a running process in Task Manager (mem.usage=5,840k, 144 handles).
XPpro,Sp2