This may help those who may be locked out as I was:
I am normally using a Wifi Router between my PC and the internet modem provide by my ISP.
As nothing was working for me and I wasn't able to overcome the
15 minutes out dreaded message, I tried removing all cookies, closing all browsers (I use 2 different ones sometimes), then I shut off PC.
After shutting down PC, I removed my Wifi Router, and set up the usual direct internet connection (ISP-provided modem -> PC), rebooted PC, opened command window (cmd), then typed
ipconfig/release, and then typed
ipconfig/renew at the command prompt in that command window. It gave me the usual ISP-provided IPaddress, and not something like 10.0.0.x which you get while using the Wifi Router.
Then I opened my Firefox, cleared history (including cookies), then tried logging in into BHW. I could log in now! (This was while using only the ISP provided modem, and not using the Wifi Router).
But then I wanted to check if I was also able to log in successfully using the wifi. So I cleared all cookies, shut off pc, added the Wifi Router between the ISP modem and PC, rebooted, opened command window, typed
ipconfig/release, then typed
ipconfig/renew... (it gave me the usual 10.0.0.x IPaddress), then I opened Firefox, cleared all cookies, tried logging in to BHW.... was able to successfully log in!
So may be the step "remove the Wifi Router, and typing first
ipconfig/release, then typing
ipconfig/renew" was needed to get over whatever bug was causing the repeated
Wait 15 minutes error.
Of course, the whole process was only a "time pass" attempt that miraculously worked for me, as I am not a pro in such matters!

, but whatever, it worked for me! May be you should also try using the same... it will at least keep you busy for a while! lol
Of course, people who are not logged in can still view this thread, so those who are still locked out may try this too (if you're also using a Wifi Router). GL!