Hi James,
Trying hard to reproduce what you describe, but I can not get those results.
What I did was on form load I update the label's text. I also added a button, which on click will update another label with form's current width and height. I then run the application, click the button and compare, then resize the browser just a little and click the button again.
This I tested with or without the post and it gives me consistent results in IE8 and FF3.6.14 for 6.4.0 Release b.
The only thing I found was if I loaded the form without the post, then edited the address and added the post, I get wrong width reported both for the initial load and the button. The button doesn't show correct width until the browser is resized.
I will report that problem when I have checked other versions of Visual WebGui.
Palli