Is the namespace really empty ? really really ? ;-)
make sure there are no deletion records enabled. They are not counted as objects and are not visible in the namespace, making him only looking empty...
If "Keep Deletion records for versioned objects" are enabled, off-click it.
If you have versioning still enabled, on-click "prune versions older than 0 days".
Then, run Garbage collection manually.
That should do it....
BR
Dirk
Is this an issue of a customer or of you, playing around with HCP and testing ?
For the latter: Does admin jvm mean something to you ? ;-)