Let me check if the .exe installer also created the proper service dependency - from the .msi installer I remember that we had to manually add a dependency to "wscsvc" (without that, it might start before the Windows Security Service itself, in which case it might fail).

edit: yes, there's a registry value missing:
HKLM\System\CurrentControlSet\Services\SBSDWSCService\DependOnService, of type REG_MULTI_SZ, needs to contain "wscsvc".