Cbdocloader error 401

We are using couchbase server for Win 64bits.
The server is running fine and we can start the web admin console perfectly.
During the installation we chose to get the sample data buckets installed but although we can see the buckets were indeed created, they are empty.
So now we are trying to use the cbdocloader tool to upload the data like so:

cbdocloader -u [user] -p [password] -b beer-sample -s 1000 ..\samples\beer-sample.zip

… but we are getting the following errors:

[2014-12-16 22:14:36,941] - [rest_client] [6352] - ERROR - http://127.0.0.1:8091/nodes/self error 401 reason: unknown
[2014-12-16 22:14:37,101] - [rest_client] [6352] - ERROR - http://127.0.0.1:8091/pools/default/buckets/ error 401 reason: unknown
[2014-12-16 22:14:37,234] - [rest_client] [6352] - ERROR - http://127.0.0.1:8091/nodes/self error 401 reason: unknown
[2014-12-16 22:14:38,283] - [rest_client] [6352] - ERROR - http://127.0.0.1:8091/nodes/self error 401 reason: unknown
[2014-12-16 22:14:39,354] - [rest_client] [6352] - ERROR - http://127.0.0.1:8091/nodes/self error 401 reason: unknown
Traceback (most recent call last):
  File "cbdocloader", line 328, in <module>
  File "cbdocloader", line 310, in main
  File "cbdocloader", line 159, in init_bucket
  File "couchbase\rest_client.pyc", line 786, in create_bucket
  File "couchbase\rest_client.pyc", line 772, in is_ns_server_ready
KeyboardInterrupt text by 4 spaces

(Note we need to interrupt the process using CTRL+C otherwise the script would run forever)
Why are we getting those 401 errors???

Thanks in advance