I had the same problem and solved it. I compared my unzipped wordpress-2.9.2.zip file with an older working version (that was moved from a previous host’s server) and the 2.9.2 version was missing most if not all the JavaScript files (.js) in the wp-includes\js folder. However, when I browsed the contents of the zip file, I could see them all in there!
All that I can figure is that the built-in zip extract program that I initially used on Windows Server 2003 is restricted or partially locked down somehow. I then installed WinRar, unzipped the 2.9.2 version with it, copied all WordPress files over (except the wp-content folder and its contents) the existing files on the web server and success!
Check your wp-includes\js folder to see if it has .js files in there.
