I'm getting an "authentication failure" error, trying to do my very first login to SalesForce. I've read the doc N times, checked out other people's postings for the same error, still can't make it work.

Here's what I did:
1) set myself up with an intro developer account on developer.salesforce.com
2) naturally, i've got admin privileges. Verified that API is enabled. Created the security token for myself and captured it.
3) set up an app:

•  enabled OA/Auth,
• set scope to 'Full Data Access", 
• set the callback URL to https://test.salesforce.com (is this right!?

4) went to "Manage" for the App and set up "Relax IP restrictions"

fired off the standard curl that everyone else uses, get nothing but "authentication failures".

Here's the CURL I'm using:

curl -v https://test.salesforce.com/services/oauth2/token \
-d "grant_type=password" 
-d "client_id=XXXXXXXXXXXXX" 
-d "client_secret=YYYYYYYYYYYYYY" 
-d "username=login@myco.com" 
-d "password=PWORDSECURITYTOKEN"    

What did I miss?