Hi,
I suspect that you also have the full version of Adobe Acrobat on your PC.That is why the data connections work on your system.
Unless you Reader Enable your form with LiveCycle Reader Extensions Enterprise Suite, then web service calls / data connections will not work in Reader.So if your users have Reader the data connections will not work on their PCs.
Here is a summary of functionality in Acrobat and Reader.
Good luck,
Niall