MsDepSvc.exe unhandled exception

I'm trying to use MSDeploy 3 RC to deploy a packaged web app to a remote Windows 2003/IIS 6 server. The deployment is controlled by a NAnt script running on a build server. The script loops through a set of 6 IIS sites on the target server and runs a sequence of MSDeploy calls for each. Essentially this is:

1. Stop App Pool
2. Deploy package with site-specific setParameters.xml file
3. Start App Pool.

However the MSDeploy service on the remote server randomly crashes with the error below. It is very rare for all 6 sites to be successfully updated. The server is fully patched using Microsoft Update.

Application: MsDepSvc.exe

Framework Version: v4.0.30319

Description: The process was terminated due to an unhandled exception.

Exception Info: System.ArgumentException

Stack:

at System.Security.Principal.WindowsIdentity.CreateFromToken(IntPtr)

at System.Security.Principal.WindowsIdentity..ctor(IntPtr, System.String, Int32)

at System.Security.SecurityContext.CreateCopy() at System.Threading.ExecutionContext.CreateCopy()

at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)