According to most Tech Support people, the most common user error message (regardless of Operating System) is ID 10T.
End-users' Corollary 1: most application failures occur between the hours of 2 and 4 am on a Sunday night - with a 6 am Monday deadline for the project.
End-users' Corollary 2: On the graveyard shift, there's no Tech Support to hear you scream!