If you get a Quota error with OpenStack, it doesn't have to be what it tell.

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For example, I've got this message because the RAM Quota was exceed:

2013-11-11 17:13:25 WARNING nova.compute.api [req-bdasdfas-f5d7-4fcd-bf1b-asdfasdf229e ba2c21dadasdfasdf1d6asdfasdfa0f bfe2db2aasdfasdfb8ea686asdfasdfb] Quota exceeded for bfe2db2aasdfasdfb8ea686asdfasdfb, tried to run 1 instances. Cannot run any more instances of this type.
2013-11-11 17:13:25 INFO nova.api.openstack.wsgi [req-bd003113-f5d7-4fcd-bf1b-asdfasdf229e ba2c21dadasdfasdf1d6asdfasdfa0f bfe2db2aasdfasdfb8ea686asdfasdfb] HTTP exception thrown: Quota exceeded: code=InstanceLimitExceeded

I didn't found a way how to see your complete usage. But you can set the quota with:

nova quota-update --ram 1024000 bfe2db2aasdfasdfb8ea686asdfasdfb
nova quota-update --security-groups 1000 bfe2db2aasdfasdfb8ea686asdfasdfb
...