The MSPIService.txt contains any errors/information logged during the scheduled data transfer (auto-update) between Web Timesheet to Microsoft Project Server or vice-versa. This file is located,

In XP or earlier:
C:Documents and SettingsAll UsersApplication Data1RepliconIntegration Manager for Microsoft ProjectAuto Update Log Files

In Vista and higher:
C:ProgramData1RepliconIntegration Manager for Microsoft ProjectAuto Update Log Files