Let’s re-evaluate where the issue is not.
It’s not the client. Why? Others are not complaining. Joe tests the client functionality throughly. The client’s code for this hasn’t changed in a while.
It’s not the fog server’s Code. Why? Others are not complaining. The fog community uses snapins heavily.
What’s left? Your server, it’s configuration, it’s environment.
Knowing that, we should start digging into what’s different about your server.
First, I would suggest upgrading to 1.4.1. Second, I’d start looking through /var/log/apache2/error_log after uploading a new snapin. I’d look for botched symlinks, misnamed directories, bad permissions, and incorrect configurations.