There is an update on Cubetube, which addresses the login issue some users have been experiencing - just recapping:
Users have registered in Cubetube (by clicking the red "Join or Log in" button, then entering their e-mail, password and nickname in the popup box);
These users confirmed that they were registered by successfully being able to log in to their accounts at Particle (Web IDE/Particle app)
These users couldn't log in using aforementioned Cubetube's "Join or Log in" button -- it would 'stick' to the popup after clicking the 'Log in' button
If you're among the people experiencing these issues, read on.
The steps to correct your issue are as follows:
Access www.cubetube.org, then click the red button (as if you would normally log in)
Enter your registered e-mail address and password in the "Log in" popup
Then click the "Log in" button (you might need to wait 1-2 seconds)
Then you will be presented with the 'Sign up' popup, it will have the e-mail and password fields already pre-populated for you
There will be a message in small red letters just above the 'Create user' button
Enter a nickname, click "Create user" and after 1-2 seconds you should be logged in!
Note: This is a one-time-only process - subsequent logins should go through the normal way, no longer asking you to reenter the nickname