I'm trying to deploy a custom Windows Service (written in C#; installed through a VS setup project) using a group policy. To help debug this, I also have two additional MSIs in the same policy. All three packages are deployed as a machine policy, not a user one.

• On one machine (runs Windows Server 2008; no UAC), all three deploy fine. The service is set to Automatic, as expected.
• On two machines (run Windows 7; UAC), the two other MSIs deploy fine, but my service fails to install. The event log gives an event ID of 102, which appears to be a permissions problem:

The install of application "Package Name" from policy "Policy Name" failed. The error was The installation source for this product is not available. Verify that the source exists and that you can access it.

However, all three packages come from the same share linked through UNC, so this is unlikely. My guess is that UAC is the problem; that the service requires additional permissions. Do I need to alter the MSI somehow?