After much research and trial and error, I have successfully upgraded a few 4.5.5. installations on different machines to 4.6.0.  I would like to share the steps I went through (some of these steps are from the tutorials of Mitchel Sellers and other postings in this forum):

• Backup the 4.5.5 installation and database
• Rename web.config to web.config.old
• Delete the entire bin folder
• Unzip the file DotNetNuke_04.06.00_Install.zip and extract the content, overwriting the files in the installation
• Delete web.config
• Rename release.config to web.config
• Open both web.config.old and web.config and do some copying and overwriting (from web.config.old to web.config)
• Overwrite the <connectionStrings> element
• Overwrite the first two <add key="SiteSqlServer"> elements
• Overwrite the <machineKey> element
• Copy the <codeSubDirectories> element and paste it in the right place
• Copy any customized configuration elements into web.config
• Use a browser and navigate to localhost/[root]/Install/install.aspx?mode=upgrade
• Three dll files are generated in Bin/Providers. Copy them and place them directly in Bin
• In the browser, navigate to localhost/[root]/Default.aspx
• Log in as the Host
• Reinstall any missing modules
• Copy any files you have touched upon for those modules (.dll, .vb, and .ascx files) and overwrite those in the 4.6.0 installation

I did not run into the Whitespace filter problem. So I will skip that. See Mitchel's discussion on this.

We havd found and copied the new authentication providers DLL.  and the folders for both Desktopmodules/AuthenticationService/LiveId  and...OpenID.  Then we discovered the new 'Authentication' table in the 4.6.0 version database has only one record for the DNN authenication.  Does anyone have the 'goods' on the other records?

Any assistance would be appreciated.

Cheers