how to reproduce:

1) have a deltacloud instance with ec2 running
2) choose "Launch instance" in the Cloud view context menu
3) choose the image you want to launch an instance of
4) in the keys, hit "Manage"
5) browse to the dir where you stored the PEM file you recieved from amazon
6) hit finish

Result:
You get an error dialog that tells you of an internal server error on the deltacloud server

Expected result:
instance could be launched

Everything works fine if I create a new key or use a key I created within the deltacloud tools.