Hi GetMem, I totally see where you're coming from. I'd have guessed that too, but I checked and it's not that.
I have no AV on my developing machine, and the company's firewall never makes a fuss about any new executable trying to reach the network. Plus I copied the executable into a test machine within the customer's network, the same place where I tested the Delphi version.
It's really strange that it should work by Delphi and not by Lazarus, but that really seems to be the case.
I would try to port it to C# but it's such a hassle, especially because in the end it's supposed to work as a Windows service so VS adds a lot of overhead to the work. I'm losing hope on Lazarus for this though.