QtWebView posts form in Linux but not in Windows

[Exeunt Omnes]

I have a Qt application that I develop in Linux (Ubuntu), using Qt Creator, and then rebuild under Windows. It uses QtWebView.

I use QtWebView to display a site (one of mine) that has dynamically-generated links that post a form to Paypal. The HTML is essentially

<a href="javascript: document.form.submit()">...</a>

<a href="javascript: document.form.submit()">...</a>

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When I compile and run this under Linux, display the page and click the links, it posts the form correctly to Paypal, which responds as it should.

However, when I rebuild the project for Windows (transferring the source as is, with a few very minor GUI differences), run it, and click the links nothing happens.

Thinking the problem may have been that the version of Qt Creator on Linux was later than the version on Windows I installed an up-to-date version (SDK version 4.8.1) on Windows but this has made no difference.

Other information

• I'm using mingw.
• The Paypal site uses SSL, of course, but as far as I can tell SSL is compiled into both the Linux and Windows versions.
• Neither the Linux version nor the Windows version allows a direct link outside the original site (<a href="http://...">...</a> or <a href="https://...">...</a>).

Does anyone have any suggestions?

Thanks!