Error Logging into salesforce.com

Problem: loggin inot apexdataloader for the first time encountered "error logging into salesforce.com

Solution: Salesforce.com released a security measures for instances when a user tries to login to Salesforce.com outside of a trusted network by making API calls from an external server using the data loader or other tools.

You will need to reset your security token before following the instructions below:

This is how you reset your token:
Log into salesforce.com website using your account. click Setup -> My Personal Information -> Reset My Security Token. Then hit the "Reset Security Token" button on the resulting page, hence you will recieve an email with your new security token and instructions similar to the instruction below:

How to enter your security token:

if your password = "mypassword"
and your security token = "XXXXXXXXXX"

you must enter "mypasswordXXXXXXXXXX" in place of your password.

I hope this solution will help you resolved your problem logging into dataloader tool.