How to create an EC2 instance with knife?

I was able to make knife access AWS by following: http://www.agileweboperations.com/amazon-ec2-instances-with-opscode-chef-using-knife

Now, I get a knife command almost working:

$ knife ec2 server create -r "role[base]" -I ami-c1aaabb5  -f t1.micro -S knife -i ~/.ssh/knife.pem --ssh-user ubuntu --region eu-west-1 -Z eu-west-1a

Instance ID: i-xxxxxx
Flavor: m1.small
Image: ami-399ca94d
Region: eu-west-1
Availability Zone: eu-west-1a
Security Groups: default
Tags: {"Name"=>"i-xxxxxx"}
SSH Key: knife

Waiting for server............................
Public DNS Name: ec2-xxxxxx.eu-west-1.compute.amazonaws.com
Public IP Address: yy.yy.yy.yy
Private DNS Name: ip-xxxxxxx.eu-west-1.compute.internal
Private IP Address: zz.zz.zz.zz

Waiting for sshd...................................

But now I get a timeout. Any ideas/suggestions how to create an EC2 instance ready for Chef provisioning?

Thanks!

My guess would be that your default security group is not allowing SSH traffic.