Have you tried to run the Dreamweaver CS5 11.03 updater and gotten a cryptic error saying that an instance of an Adobe product is open? Don't have any other Adobe products open?

 

I've run into this a couple of times on WinXP pro until I found this solution: Provided that you have admin rights on your machine, go into Control Panel-> Administrative Tools-> Services.

 

Make sure that the "Workstation" service is turned on, if it isn't start it. Once it starts, run the updater again and the problem should go away