The salesforce.com Web services are not accessible to the user whose credentials you provided. The most likely cause is that ...

The salesforce.com Web services are not accessible to the user whose credentials you provided.  The most likely cause is that the user is not an administrator of a Salesforce edition that permits Web service access.  Web services are only accessible from Developer, Enterprise, Sandbox and Unlimited editions of Salesforce.  

Developer editions are available free of charge from Salesforce.com's Developer Community site.  The free trial editions of Salesforce that are available from Salesforce.com's home page are not Developer editions.     

If your user is an administrator of a Salesforce edition that permits Web service access, then it is possible that Web service access had been disabled for that user.  For Web service access to be enabled for a user, that user must have a Salesforce Profile for which API Access is enabled.  Follow these steps to ensure that setting is indeed enabled for your user: 
1.  Log on to Salesforce.  
2.  Choose Setup from the User Menu that is a drop-down list under your user name, on the top right side of the screen.  
3.  Use the menu on the right to navigate to Personal Setup|My Personal Information|Personal Information.   
4.  Find the link to your user's Profile and click on that link.  
5.  Under the Administrative Permissions section, ensure that the API enabled option is selected