Hi Mathias!
The bug doesn't occurs if I use UT URL.
If I navigate to the VFPX URL, for example, the bug occurs.
I'll try to find whats happening.

Updated:
It seems to be a focus issue...
UT site set the focus to the textbox to specify the user and the page is displayed as expected.
If I navigate to another URL that don't receive the focus, the page isn't displayed (as you reported).
If I force the focus to the WebBrowser control, the page is displayed as expected.
I also tried the same with VFP native controls and the same problem occurs.
So, this isn't a TC issue.

Try to create a form and place a label, a textbox, a command button and a container.
Place WebBrowser control inside the container.
Be sure that the tab order is: label 1, textbox 2, command button 3 and container 4.
Place the code to navigate to http://www.codeplex.com/VFPX in the init of the form.
Run the form and you'll see that the page isn't displayed.

Regards