I had the login problem only when I use a different PC, Smartphone, ...
The following instructions have solved my problem:
1. I typed in my existing login and password
2. Then came "Click to proceed", so I clicked on it
3. I'm not sure but either got an error message or I ended up back at the login
4. Back at the login screen, again I typed in my existing login and password
5. When step 3 is reapeated, I opened the link
http://www.the-minimizer.com/forum_3/ again
6. I was logged in!