Are you having troubles getting Steam to boot up today? If so, the problem might not be with Valve's blockbuster gaming service; the issue could be your antivirus, instead. This weekend, the freebie Avast! antivirus misidentified a Steam component as a nasty little Trojan and sent the executable to the time-out box known as Quarantine as a result. The problem: SteamService.exe was a totally clean file, and Steam won't run without it.