Are you using mapped drives or UNC paths on the terminal server?

Mapped for Programs, and UNC for SharedData.

Where is Programs stored?

Where SharedData stored?

On the same terminal server or a different server(s)?

We just inherited this client. Installation was done by another consulting company a few years ago.

Programs is under: C:\Accpac

SharedDate is under: \\AnotherServer\Accpac\Accdata

Ok, take out the mapped drive to Programs and use C:\Accpac instead. Mapped drives are obsolete. But you will have to uninstall/reinstall to that, so focus on the main issue first, which is SharedData.

The problem though is with the SharedData, check that you have access to SharedData and that you can create a text file in SharedData and then delete the file. Do the same in the Site folder.

Humm.... just noticed something interesting: there is no SITE folder under C:\Accpac.

when logon with user XYZ via RDP from Win7, I get error. But when logon with user XYZ via RDP from Win8, no error.

That's because SITE is under SharedData.

Sorry, my bad, I was looking for something else.

Anyways, so why this error is "remote workstation" specific, even with same login account?

Have you checked this:

"The problem though is with the SharedData, check that you have access to SharedData and that you can create a text file in SharedData and then delete the file. Do the same in the Site folder."