IDE/BoardPackage Install Got Whacked

I attempted to install a beta ESP8266 board package (v2.4.0-rc2) , and the attempt seems to have completely whacked my IDE installation. While the ESP8266 boards DO show up in the Boards menu, and the library IS installed in the correct packages subdirectory within AppData\local\arduino15, ANY attempt to compile using ANY 8266 board gives an error message that neither the platform nor board are known. I'm guessing that package_index.json has been corrupted, or at least not correctly updated, but I am at a loss to know how to get things working again. I've uninstalled the offending package, and re-installed the previous one that WAS working (v2.2.0), but to no avail. It's still broken.

Is there any way to fix this other than doing a fresh re-install of the whole IDE/board packages and everything else?

I REALLY wish it was easier to understand HOW all this stuff is tied together. Seems like I spend about more time lately fighting the vagaries of the IDE, the goofy build process, and serious bugs, than actually writing code....

Regards, Ray L.

Please describe the exact process you followed to install v2.4.0-rc2. If you found instructions somewhere then you can post a link to them.

I have no clue what went wrong. I ended up ditching my whole Arduino installation, and recreating it from scratch. It came out fine the second time, and the beta ESP package gave me the feature I needed - being able to setup the softAP for 8 connections, rather than 4.

Regards, Ray L.