Paypal express checkout not working

I'm trying to setup paypal express checkout on my website. I've followed the steps described on the forum but I still get the following error

We are sorry for the inconvenience. The PayPal account authentication settings are not yet set up, or the API security information is incorrect. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002) 10002 Security error - Security header is not valid

On further following the wiki help I tested following

1. CURL Test - Succeds

https://vaasvara.com/catalog/extras/curltest.php - success
https://vaasvara.com/catalog/extras/curltest.php?ssl=1 - fail
https://vaasvara.com/catalog/extras/curltest.php?ssl=1&proxy=1 - success

2. ipnconfig test - Fails for SSL; succeds for SSL

https://vaasvara.com/catalog/extras/ipncheck.php

the ipnconfig and I get the following error

IPNCHECK.PHP - Version 1.0

IPN TESTING - POSTING to PayPal via: ssl://www.paypal.com:443

Warning: fsockopen() [function.fsockopen]: unable to connect to ssl://www.paypal.com:443 (Connection timed out) in /home/content/v/i/n/vinaymolasi/html/catalog/extras/ipncheck.php on line 81
IPN FATAL ERROR :: Could not establish fsockopen.
Host Details = ssl://www.paypal.com:443 (110) Connection timed out

Trying again without SSL ...

IPN TESTING - Confirmation/Validation response: RESPONSE RECEIVED - Communications OKAY

Script finished.

3. The site is hosted on godaddy.com. and the SSL certificate is installed

4. allow_url_fopen = on is set in php.ini

5. Error Log from Paypal Log directory - attached.

6. Website address - http://vaasvara.com/catalog

7. Payment Modules installed

• Paypal Express Checkout (Sandbox)
• PayPal IPN - Website Payments Standard

vmolasi:

We are sorry for the inconvenience. The PayPal account authentication settings are not yet set up, or the API security information is incorrect. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002) 10002 Security error - Security header is not valid

This means, as it says, that you've entered invalid information for the API username/password/signature fields in your module settings, and/or you've selected "sandbox" when it should be "live" or vice-versa.

You're right on. I was using Sandbox setting with Production server username. So the cart is getting redirected to the Paypal-website and the basic flow seems to be working fine. But the ipncheck.php still fails fo SSL check. Is this because of the proxy serve requirement by go-daddy?

GoDaddy does weird things, so, the answer is "maybe -- most-likely".