1606, as I have found is a com error during a network look-up, I have yet to determine anything outside of the fact that Vista uses domain controllers and services for the greater part of the O.S. for security reasons. Tis the old school way of the logical client - server model.
Unfortunately I incurred the same problem without resolve with support. I performed cleanup with specialized tools from Microsoft, and ended up using a 3rd party un-installation program and manually editing registry keys. My system was still operational as I'm not a fool when in the registry but, 1606 haunted anything .Net Framework oriented.
I eventually re-installed and reverted from Vista Ult. to XP Home and will stay there until I get Win7 Ult.
Have a hard time installing anything that relies on the .Net Framework don't you?
You'll have just as much trouble trying un-install anything reliant on the framework as well.
Definitely think I got an idea that it isn't entirely at the fault of the Microsoft Software Installer (.msi) but, there were indications.
You might have to seriously consider re-installation of Vista or a serious rollback.
Hope this little bit of insight will save you some aggravation -- as I was gritting my teeth for about two weeks over the ordeal and to no avail.
Take it easy.