m4000

Hi!
I'm having the website www.sol-eye.com. (I don't get that much orders via the website, but they come now and then.)
This Monday I got two orders that worked. Yesterday, I got e-mails that said:

"Paypal Express Debug E-Mail" in the subject line, and the message was:
$HTTP_POST_VARS:
$HTTP_GET_VARS:

This morning I tried my self to buy some items, and pressed the buy button to continue to Paypal website. Noting happened, except the debug e-mail.

In the admin, I clicked the "Test API Credentials" link under "PayPal Express Checkout".
After a few minutes I got the following info:

Failure!
The PayPal Express Checkout credentials are not set up correctly for live production use.
array(0) {
}

This is very strange, because everything worked this Monday (and everything has worked since summer 2011), and yesterday it stopped working. And I haven't touch any settings or anything.

Please - need some help and suggestions.

Thank you!