The GNU screen is unresponsive, seems blocked

In the commands below, replace Ctrl with whatever your escape key is for screen commands.

Try Ctrl+a q, which is the sequence to unblock scrolling.

Ctrl+a s is the sequence that blocks scrolling, which makes screen seem like it freezes.

When using PuTTY, you can get an apparently freezed screen if you press Ctrl+s. This sends an Xoff signal blocking the terminal's output.

The solution is to press Ctrl+q to send the Xon signal.