If nothing in the blog helps AND the problem doesn't "fix itself" contact the staff directly by clicking on Help & Support at the bottom of the page
BTW it would help if you described your OS, browser and ISP connection - a "fast cable connection" means nothing to me, how am I supposed to know what your idea of "fast" is?
http://blog.chess.com/NimzoRoy/diagnosing-and-fixing-internet-problems
For the last few days I've tried playing the Tactics Trainer, and I'd make a move or two, then it would come up with a green or blue button indicating it was my move. But it was the computer's move. There was no way I could enter a move, and I ended up leaving the site. I thought it might be because I was piggy-backing on my neighbor's WiFi connection (with her permission).
But today I got home to my regular computer with a fast cable connection, and I'm getting the same problem--freezing up and not letting me move on.
What's going on?
BTW, Chess Tactics Server (free) NEVER freezes up. Just saying.