I'm having the exact same problem as Tennant. I'm running Windows Vista Ultimate 64-bit. I have MSI logs, attempted to separately run the
Cassini Explorer and
Cassini Server 2 Setup installers. Both times I see "The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2869."
This was done in an attempt to install UltiDev Cassini after installation failed from WebGuide. Or rather, install said it was successful, but it turns out the product never installs: the service is not available, no reference to Cassini is made in Start | Programs. Multiple attempts to install (repair WebGuide installation) and download 64-bit version of Cassini that supports .NET 2 have failed so far. I also get the same error Tennant sees in the Event Viewer.
Any suggestions, steps, etc. appreciated.