PayPal Direct Payment Error 10747

Hi everyone, I've been getting this error for the past week:

ALERT: PayPal Direct Payment Error (10747 <!-- -->)
10747 Invalid Data - This transaction cannot be processed.

I looked up the error code on the PayPal site and found it was due to an invalid IP address. I tried looking for the IP to check it but couldn't find anything in Zen Cart or my files. Has anyone had this error before, or can anyone point me in the right direction? This is really urgent.
Any help will be much appreciated.
Thanks in advance

Please turn on debug logging in your PayPal module, and post the log files that contain "CURL" in the filenames.
http://www.zen-cart.com/forum/showthread.php?t=61199

I have 100+ log files, so here's the most recent one.

2009-06-29 03:17:21

(live transaction) --> https://api-3t.paypal.com/nvp
Request Headers:
Array
(
[0] => Content-Type: text/namevalue
[1] => X-VPS-Timeout: 45
[2] => X-VPS-VIT-Client-Type: PHP/cURL
[3] => X-VPS-VIT-Integration-Product: PHP::Zen Cart - WPP-NVP
[4] => X-VPS-VIT-Integration-Version: 1.3.8a
)

Request Parameters: {DoDirectPayment}
Array
(
[ACCT] => ************6714
[AMT] => 205.00
[BUTTONSOURCE] => ZenCart-DP_us
[CARDISSUE] =>
[CITY] => Lebanon
[COUNTRYCODE] => US
[CREDITCARDTYPE] => MasterCard
[CVV2] => ***
[EMAIL] => mkumar12345######################
[EXPDATE] => 112010
[FIRSTNAME] => Manish
[IPADDRESS] => unknown
[ITEMAMT] => 197.00
[LASTNAME] => Kumar
[L_AMT0] => 197.00
[L_NAME0] => OQ Ring Titanium Size: D
[L_NUMBER0] =>
[L_QTY0] => 1
[L_TAXAMT0] => 0.00
[NOTIFYURL] => http://www.oqring.com/store/ipn_main_handler.php
[PAYMENTACTION] => Sale
[PHONENUM] => 315-345-6420
[SHIPPINGAMT] => 8.00
[SHIPTOCITY] => Lebanon
[SHIPTOCOUNTRYCODE] => US
[SHIPTONAME] => Manish Kumar
[SHIPTOSTATE] => NH
[SHIPTOSTREET] => 59 Prospect Street
[SHIPTOSTREET2] => Apt # 2
[SHIPTOZIP] => 03766
[STATE] => NH
[STREET] => 59 Prospect Street
[STREET2] => Apt # 2
[ZIP] => 03766
[METHOD] => DoDirectPayment
[CURRENCYCODE] => USD
[USER] => young143kr_api1.gmail.com
[PWD] => ****************
[VERSION] => 2.3
[SIGNATURE] => ****************************************************9nuD
)

Response:
Array
(
[TIMESTAMP] => 2009-06-29T19:17:23Z
[CORRELATIONID] => 963bc62aca3e0
[ACK] => Failure
[VERSION] => 2.3
[BUILD] => 950845
[L_ERRORCODE0] => 10747
[L_SHORTMESSAGE0] => Invalid Data
[L_LONGMESSAGE0] => This transaction cannot be processed.
[L_SEVERITYCODE0] => Error
[AMT] => 205.00
[CURRENCYCODE] => USD
[CURL_ERRORS] =>
)

DoDirectPayment, Elapsed: 928ms -- Failure

TIMESTAMP=2009%2d06%2d29T19%3a17%3a23Z&CORRELATIONID=963bc62aca3e0&ACK=Failure&VERSION=2%2e3&BUILD=950845&L_ERRORCODE0=10747&L_SHORTMESSAGE0=Invalid%20Data&L_LONGMESSAGE0=This%20transaction%20cannot%20be%20processed%2e&L_SEVERITYCODE0=Error&AMT=205%2e00&CURRENCYCODE=USD&CURL_ERRORS=

ohcue:

Response:
(
[TIMESTAMP] => 2009-06-29T19:17:23Z
[CORRELATIONID] => 963bc62aca3e0
[ACK] => Failure
[VERSION] => 2.3
[BUILD] => 950845
[L_ERRORCODE0] => 10747
[L_SHORTMESSAGE0] => Invalid Data
[L_LONGMESSAGE0] => This transaction cannot be processed.
[L_SEVERITYCODE0] => Error
[AMT] => 205.00
[CURRENCYCODE] => USD
[CURL_ERRORS] =>
)
I would be reporting it to PayPal support and asking their input, since it's their server that's rejecting the transaction.
If, as you say, it's related to IP address, then perhaps they're rejecting the customer's IP? Best to ask PayPal directly: https://www.paypal.com/mts