error message at checkout with Paypal

I get the following error message when I try to checkout with Paypal. I think I know what it's referring to: I uploaded my own logo in Paypal connecting to a file on a secure server. Do have any idea what the error message means? Thanks, Joe.
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There was a problem connecting to PayPal to setup your purchase. Please try again.
10002 - Security error - Security header is not valid