PuTTY pscp.exe now requires explicit port flag -P 22 normally
pscp -i your.ppk -P 22 ec2-user@your-ec2-ip:/home/ec2-user/your-file-to-download .
At least this works for me. In the past it worked without the -P 22, I believe this is a new feature / requirement of newer versions of PuTTY.