Stdin error

[g5pw]

After ~500 characters are read, the server locks and I cannot send any more messages.

[5p4k]

As you can see from the source code, data is read from STDIN using input_raw() function, and then plugged into the crypto system.
I've been running test: after around 500 characters are typed, you can't write anything more; this includes the CR or LF characters necessary to end the line and exit the input_raw() function. Press one or twice backspace and you'll be able to type return and end the line, avoiding the apparent lock.
Therefore this is not a problem concerning PyEC implementation but the input_raw() function.

I encourage you to fork the project and replace the input system with your own: I'll be looking forward for a pull request.