I redid it again and then did a stop/start sps service... I then tried to unregister, again without success.
Here's the result of the 'UnregisterProvider_Task':
Method Invocation Result: ManagedObjectReference
| Name | Type | Value |
|---|---|---|
| dynamicProperty | ArrayOfDynamicProperty | Unset |
| dynamicType | string | Unset |
| name | string | Return value |
| val | anyType | SmsTask-52 |