Create a bucket with GSUtil causing problems

Mac OSX 10.8.2

Following https://developers.google.com/cloud-sql/docs/import_export#importing - 

Importing and Exporting Data.

Step 3 of Upload your existing MySQL database to Google Cloud Storage: is causing following error:-

Thomas-Duffys-MacBook-Air:tom tom$ gsutil mb gs://bucket_tom

Creating gs://bucket_tom/...

GSResponseError: status=400, code=MissingSecurityHeader, reason=Bad Request, detail=Authorization.

Thomas-Duffys-MacBook-Air:tom tom$ 

Any help would be appreciated.