[ec2] Network packet loss after trying to upgrade to 9.04

[Alessandro Alinone]

I apologize in advance for my silly question, but I'm a newbie.

I launched an EC2 instance with the Official Ubuntu Release 8.10 Intrepid
(Europe, 32 bit server): ami-80c0e8f4.

Then I logged in and upgraded to Ubuntu 9.04 through this command:
sudo do-release-upgrade

I accepted all the default options. I rebooted the instance and the
upgrade seemed fine. But then I started seeing the SSH terminal slower
and slower. I launched a train of ping from different locations in the
world and noticed high rates of packet loss (around 50%).

I launched a second EC2 instance with the same Official Ubuntu Release,
but without upgrading it. The SSH terminal was fast and the ping tests
showed no packet loss. I had the two ping windows side to side,
showing quite different behaviors.

Any idea of how to explain this?

By the way, the average round-trip time was the same in both cases;
only the packet-loss rate is quite different.

When will the official 9.04 AMI be available?

Thanks

-Alessandro