After all the things I've tried and suggestions received from various
people....

The backup and restore idea did not fly. The back up (with force overwrite
option) could not overwrite the old dll.

The solution is...

1. Extract the IB install files to a folder.
2. Overwrite the old (bad) dll with a new (good) dll.
3. Install IB.

That works even if IB was previously installed or a fresh install.

It seems simple enough to supply this dll with the IB install pack.

Shiv.