Exton: That's because I reinstalled from scratch, so you got in just before I changed the passwords. The problem was never resolved.
I have figured out who caused it, but not what caused it. Over last weekend Network Solutions have upgraded their plans and control panel. It now includes an automated script for installation of DotNetNuke (regretably it's version 4.5.3). Typical for Network Solutions they are always behind everyone else. In addition, if you use the automated scripts to install DNN they make you install it into a subfolder, i.e. {domain}/yourdnnfolder, it doesn't go into your root folder. And, on top of that, they use an internal MSSQL server for the DNN installs, which makes it impossible to connect to the DB externally via SQL Server Management Studio. All in all, a very crappy job by Network Solutions. Very disappointing.
Regarding the error, I suspect that during their upgrades they have changed something that is messing up some permissions for execution of the code of the Login control. I have another DNN installation with them on another account, but it's version 4.5.5 and it's not affected by what they did. However, version 4.8.0 which is what the cci-leadershipstrategies.com was running before the problem appeared, does not run. I tried installing it again from scratch, without the wizard and as soon as the installation was complete the first time I clicked "Login" I got the same error as my original post.
DotNetNuke core team: any ideas what they may have done to cause the login control to break???
Jeremy Nichols: Since you say you host with Network Solutions, too, then your problem is the same as mine. If you succeed in resolving it with their help or in any other way please share the info. I'd like to be able to install 4.8.0 and for it to work like before they did the upgrade. This has cost me hours and hours of extra work. Maybe I should bill Network Solutions for that! Ha!
Exiton wrote
I can see the login form. I even managed to log in as admin. :)