Hello!
LoadUI is developed on Windows 7 and since it runs in the Java Virtual Machine, there's no reason why its functioning should differ between different operating systems.
There's most likely something else that the operating system that differs between the two systems you are referring to (e.g. firewalls, proxy settings, local network domain).
Which component in loadUI are you using to make the requests? Web Page Runner? SoapUI Runner?
If you are using a Web Page Runner, try open the same web address in a web browser.
If you are using a soapUI Runner, try running the same soapUI TestCase in soapUI on the same computer.
Regards
Henrik
eviware