Even if it's old, I would try with this version if Qt to see if you have the same issue going on.

Thank you all. The problem is solved I think. I up vote all answers to appreciate your help.

same client and server setup, but different out put sounds very strange...
I would suspect some misconfiguration on the VM webserver.
But here are some thoughts:

Some servers also behave strange when no USER-AGENT header is sent with the request Is the javascript embedded`/inlined or referenced externally as file in the yhead> section? what do the IIS logs tell?

Looks good.

Then, you should use gdb to debug your application