Your internet connection was probably bad.
How did this happen??

There's "full" and then there's "FULL" internet connections.
sftac
ps. By any chance, was 'WiFi' involved? Or, do you have any software on your PC? I ask the second question because sometimes autoupdating (of Windows, Anti-Virus software, Flash, etc.) will 'take over' your connection at the expense of other stuff like chess.com
yeres30, thanks. Just weird because in the second round, my opponent did not make their first move in time, yet it had been about 5 minutes already.
I'm playing in a tournament right now. I won the first two rounds. The second round, my game was taking a while to load. After about two minutes, it said I had lost the game. By the way, it was a 10/0 tournament. Free (fake) candy for anyone who answers my question with a good reply! Thanks!