Connecting to Amazon EC2 - connection timed out

hi everyone,
I'm trying to connect to my instance on Amazon EC2. I've read a few posts here and there and I believe I'm doing everything right, except I constantly get the connection timed out error.

I'm running Filezilla 3.6.0
I'm running filezilla from a virtual server inside our network.
I have specified my Amazon key pair in the filezilla settings under SFTP
I have entered in my host using my public DNS
I have specified the user to be ec2-user.
I have opened up ports 20-23 on my amazon security groups for 0.0.0.0/0 and specifically port 22 for 0.0.0.0/0

Status: Connecting to ec2-###-###-###-###.us-west-1.compute.amazonaws.com...
Response: fzSftp started
Command: keyfile "S:\Administrative\AmazonCloud_ArcGIS\PEM_To_FileZilla.ppk"
Command: open "ec2-user@ec2-###-###-###-###.us-west-1.compute.amazonaws.com" 22
Error: Connection timed out
Error: Could not connect to server

Are there any suggestions as to what may be blocking my connection?? have spent about 4 hours now trying to get this to work - has to be something simple that I'm missing?
Thanks for any suggestions.
Steve

*EDIT* - I just connected to another FTP server not on Amazon with no issues whatsoever.