Probably some connection issue. Before you start changing stuff, try rebooting your pc, in 90% of all cases it helps to solve any computer problem.
If that doesn't help, it's probably your connection that's bugging you. Are you sure your router/firewall/antivirus isn't blocking it? I know, this is impossible normally (since you probably could play perfectly until some point), but sometimes virusscanners have their own behavior...
Else, I'd just advice you to wait for an hour or so, and see if it's solved.