Until - - Microsoft stopped supporting IIS 6 and my provider downgraded to IIS 7 !!!
The problem is the new "security" rule - URLs which contain a plus sign no longer work.
As a result, directories containing "c++" in the name no longer work.
To be perfectly clear - this is the kind of behavior I expect from a virus. My site was broken! and if I had not stumbled on to an affected page, I would have never known.
/Languages/Borland_C++ /Languages/C++_Builder /Languages/Console_C++ /Languages/VisualC++
To manually "fix" this would have required editing every file that references any of these. This is much worse than most viruses.
Instead, I created and uploaded the new configuration file (next section) and my site is now functional. (The Microsoft intentional attack was undone.)
It only took about a day to find this, and even then, I had to modify what I found. Basically
I give Microsoft credit for providing a way to disable their !@#$%, but I firmly believe that they knew what they were doing and that this change was to intentionally cause problems. The fact that my ISP's help desk had no knowledge of this issue, and that customers were not notified that their sites would be affected, also supports my conclusion.