I have found this message into a log file in ProgramData Folder
11/22/2012 14:01:11 ERROR ============== SERVICE STARTING ===============================
11/22/2012 14:01:11 INFO Using server mode garbage collector
11/22/2012 14:01:11 ERROR Exception initializing context: Could not load file or assembly 'System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.
11/22/2012 14:01:11 ERROR Failed to initialze View Topo context, stopping the service