When I post my solution, I get local references in the error report.

Okay. I've made some headway here. When I added the FirstData solution to the NopCommerce solution in the folder payment, it created an absolute path for the solution, not a relative path. I've changed the path from

[ C:\Users\lpolitis.TBC\Desktop\FirstData_1.6\NopCommerce_FirstData_1.6\Payment\Nop.Payment.FirstData\ ]
  to
[ C:\Users\lpolitis.TBC\Desktop\FreeLance\FloMo_eStore\Payment\Nop.Payment.FirstData\ ]

And now I get this result.
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Error during payment processing .......................................... RESP:

myErrorMessage:

Unable to load DLL 'lpssl.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)

myErrorNext:

System.DllNotFoundException: Unable to load DLL 'lpssl.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E) at LinkPointTransaction.LPSSL_Wrapper.lp_send(String inXml, String clientCertPath, String host, Int32 port, String outXml, Int32 outLen, String logFile, Int32 logOpts) at LinkPointTransaction.LinkPointTxn.send(String sXml) at LinkPointTransaction.LinkPointTxn.send(String sClientCertPath, String sHost, Int32 iPort, String sXml) at NopSolutions.NopCommerce.Payment.Methods.FirstData.FirstDataPaymentProcessor.SendPaymentInfoAndGetResponse(LPOrderPart orderFD) in C:\Users\lpolitis.TBC\Desktop\FreeLance\FloMo_eStore\Payment\Nop.Payment.FirstData\FirstDataPaymentProcessor.cs:line 361 myErrorStackTrace at LinkPointTransaction.LPSSL_Wrapper.lp_send(String inXml, String clientCertPath, String host, Int32 port, String outXml, Int32 outLen, String logFile, Int32 logOpts) at LinkPointTransaction.LinkPointTxn.send(String sXml) at LinkPointTransaction.LinkPointTxn.send(String sClientCertPath, String sHost, Int32 iPort, String sXml) at NopSolutions.NopCommerce.Payment.Methods.FirstData.FirstDataPaymentProcessor.SendPaymentInfoAndGetResponse(LPOrderPart orderFD) in C:\Users\lpolitis.TBC\Desktop\FreeLance\FloMo_eStore\Payment\Nop.Payment.FirstData\FirstDataPaymentProcessor.cs:line 361
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How can I get it to refer to the solution relatively, not absolutely? Am I not including it in the build for some reason?

Here's how it's referred to in the NopCommerce.sln file:
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Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Nop.Payment.FirstData", "Payment\Nop.Payment.FirstData\Nop.Payment.FirstData.csproj", "{6F4C4D28-1520-451E-8522-2660895EC30D}"
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It doesn't refer to the absolute path.

Any suggestions, guys? I really need to get this working.

Sorry, work during the day, do side projects at night.

What are you running for a web server? I've had a problem with older libraries running on Windows Server 2008 & R2. Also, did you make sure the lpssl.dll file is in your /bin directory.

As for the other questions, the pathing that you are seeing on errors is normal. If I build a library and give it to you and it throws an exception, you would see the pathing on my computer where I built the library. So, at this point I wouldn't necessarily worry about that.

Let me know. I'll be here or in EVE. :)

Mike

I'm running Windows Server 2008 R2 with SQL Management Studio Express, IIS 7 (defaultapp pool:  2.0x xx framework, Integrated Pipeline) the lpssl.dll is in the folder it should be.

http://lakipolitis.com/redux_images/lpssl.png

I was able to fix this by adding lpssl.dll to the path.  To do this you have one of two options:

1. Copy lpssl.dll to a folder that is already in the path.  You can see what folders are in the path by typing 'echo %PATH%' at a command prompt.

OR

2. Add the folder that lpssl.dll is in to the path.  To do this, right-click on My Computer, then Properties, then Advanced System Settings, then on the Advanced tab click 'Environment Variables', then in the lower box with 'System Variables' find the 'Path' variable and double-click it.  If your lpssl.dll is at c:\myprojects\coolwebsite\bin\lpssl.dll, then you want to append this to the end of the current path string (starting with adding a semicolon to separate it from the previous paths:   ;c:\myprojects\coolwebsite\bin

I've written more about my troubles with the LinkPoint pieces on my blog at
http://adventuresindotnet.blogspot.com/2012/02/linkpointtransactiondll.html